Astronomy User's Library

The following is a listing of the entire contents of this library for IDL. Click on an individual procedure name to view its header and source code. This listing is a shortened form of the much longer entire library help file. This may be handy for text searchs, be beware that some of these are huge and may take a long time to load or even crash your browser.

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Last modified: Thu Dec 21 21:14:28 2000.

List of Routines

ABSCAL Apply the FITS BZERO and BSCALE keyword values to a data array
AD2XY Compute X and Y from RA and DEC and a FITS astrometry structure A tangent (gnomonic) projection is computed directly; other projections are computed using WCSXY2SPH. AD2XY is meant to be used internal to other procedures. For interactive purposes, use ADXY.
ADSTRING Return RA and Dec as character string in sexigesimal format. RA and Dec may be entered as either a 2 element vector or as two separate vectors (or scalars). One can also specify the precision of the declination in digits after the decimal point.
ADXY Use a FITS header to convert celestial (RA,Dec) to pixel coordinates Use an image header to compute X and Y positions, given the RA and Dec in decimal degrees.
AFHREAD Subroutine of WFPCREAD to read a GEIS header from an HST STSDAS image. This procedure reads a GEIS header from an HST image. It then looks if a .SHH file is present for FOC images to calculate better astrometry by getting the current PSANGLV3 from this file. Called by
AIRTOVAC Convert air wavelengths to vacuum wavelengths Wavelengths are corrected for the index of refraction of air under standard conditions. Wavelength values below 2000 A will not be altered. Uses the IAU standard for conversion given in Morton (1991 Ap.J. Suppl. 77, 119)
AITOFF Convert Right Ascension, Declination to X,Y using an AITOFF projection. This procedure can be used to create an all-sky map in Galactic coordinates with an equal-area Aitoff projection. Output map coordinates are zero longitude centered.
AITOFF_GRID Produce an overlay of latitude and longitude lines over a plot or image The grid is plotted on the current graphics device. AITOFF_GRID assumes that the ouput plot coordinates span the x-range of -180 to 180 and the y-range goes from -90 to 90.
APER Compute concentric aperture photometry (adapted from DAOPHOT) APER can compute photometry in several user-specified aperture radii. A separate sky value is computed for each source using specified inner and outer sky radii.
ARCBAR Draw an arc bar on an image showing the astronomical plate scale
ARROWS To display "weathervane" directional arrows on an astronomical image Overlays a graphic showing orientation of North and East.
ASTDISP Print astronomical and pixel coordinates in a standard format This procedure (ASTrometry DISPlay) prints the astronomical and pixel coordinates in a standard format. X,Y must be supplied. RA,DEC may also be supplied, and a data number (DN) may also be supplied. With use of the Coords= keyword, a string containing the formatted data can be returned in addition or instead (with /silent)
ASTRMFIX Calculate a rough HST WFPC or FOC astrometry solution This program will calculate a rough HST WFPC or FOC astrometry solution using the keyword PSANGLEV3 which gives the angle of the V3 axis of HST. Called by WFPCREAD.
ASTRO Interactive utility for precession and coordinate conversion.
ASTROLIB Add the non-standard system variables used by the IDL Astronomy Library Also defines the environment variable or VMS logical ASTRO_DATA pointing to the directory containing data files associated with the IDL Astronomy library (system dependent).
AVG Return the average value of an array, or 1 dimension of an array Calculate the average value of an array, or calculate the average value over one dimension of an array as a function of all the other
A_B Compute B band interstellar extinction according to the RC2. The predicted B band extinction is computed as a function of Galactic position using the 21 parameter function given by deVaucouleurs in the 2nd Reference Catalog of Galaxies (RC2). Note that this formula is no longer used in the RC3 and that reddenings are instead obtained from the Burstein-Heiles 21 cm maps.
BARYVEL Calculates heliocentric and barycentric velocity components of Earth. BARYVEL takes into account the Earth-Moon motion, and is useful for radial velocity work to an accuracy of ~1 m/s.
BLINK To allow the user to alternatively examine two or more windows within a single window.
BOOST_ARRAY Append one array onto a destination array Add array APPEND to array DESTINATION, allowing the dimensions of DESTINATION to adjust to accomodate it. If both input arrays have the same number of dimensions, then the output array will have one additional dimension. Otherwise, the last dimension of DESTINATION will be incremented by one.
BOXAVE Box-average a 1 or 2 dimensional array. This procedure differs from the intrinsic REBIN function in the follow 2 ways:
BPRECESS Precess positions from J2000.0 (FK5) to B1950.0 (FK4) Calculates the mean place of a star at B1950.0 on the FK4 system from the mean place at J2000.0 on the FK5 system.
BREAK_PATH() Breaks up a path string into its component directories.
BSORT Function to sort data into ascending order, like a simple bubble sort. Original subscript order is maintained when values are equal (FIFO). (This differs from the IDL SORT routine alone, which may rearrange order for equal values)
CCM_UNRED Deredden a flux vector using the CCM 1989 parameterization The reddening curve is that of Cardelli, Clayton, and Mathis (1989 ApJ. 345, 245), including the update for the near-UV given by O'Donnell (1994, ApJ, 422, 158). Parameterization is valid from the IR to the far-UV (3.5 microns to 0.1 microns).
CHECK_FITS Check that keywords in a FITS header array match the associated data Given a FITS array IM, and a associated FITS or STSDAS header HDR, this procedure will check that (1) HDR is a string array, and IM is defined and numeric (2) The NAXISi values in HDR are appropriate to the dimensions
CHECK_TAPE_DRV Associates tape drive numbers with device files. *Unix only* This is an internal routine to the CDS/SERTS Unix tape handling utilities. It converts tape drive numbers to actual device names, and checks to make sure that the device file is open.
CIC Interpolate an irregularly sampled field using Cloud in Cell method This function interpolates an irregularly sampled field to a regular grid using Cloud In Cell (nearest grid point gets weight 1-dngp, point on other side gets weight dngp, where dngp is the distance to the nearest grid point in units of the
CIRRANGE To force an angle into the range 0 <= ang < 360.
CLEANPLOT Reset all plotting system variables (!P,!X,!Y,!Z) to their default values Reset all system variables (!P,!X,!Y,!Z) which are set by the user and which affect plotting to their default values.
CNTRD Compute the centroid coordinates of a stellar object using the algorithm in the DAOPHOT FIND subroutine.
COMPARE_STRUCT Compare all matching tag names and return differences Compare all matching Tags names (except for "except_Tags") between two structure arrays (may be different struct.defs.), and return a structured List of fields found different.
CONCAT_DIR To concatenate directory and file names for current OS. The given file name is appended to the given directory name with the format appropriate to the current operating system.
CONS_DEC Obtain the X and Y coordinates of a line of constant declination Returns a set of Y pixels values, given an image with tangent projection astrometry, and either (1) A set of X pixel values, and a scalar declination value, or (2) A set of declination values, and a scalar X value
CONS_RA Obtain the X and Y coordinates of a line of constant right ascension Return a set of X pixel values given an image with astrometry,
CONVOLVE Convolution of an image with a Point Spread Function (PSF) The default is to compute the convolution using a product of Fourier transforms (for speed).
CONV_STSDAS Convert internal format of an STSDAS image to host machine architecture Converts the internal format of an STSDAS image (.hhh and .hhd file) to the host machine architecture. Useful for copying STSDAS files between different machines. If the host is not a VMS machine, then by default CONV_STSDAS assumes the image originated on VMS. If the host is VMS, then CONV_STSDAS assumes that the image originated on an IEEE machine (e.g. SparcStation).
CONV_UNIX_VAX To convert Unix IDL data types to Vax IDL data types. CONV_UNIX_VAX assumes the Unix IDL data type is IEEE standard in either big-endian or little-endian format.
CONV_VAX_UNIX To convert VAX IDL data types to UNIX (Sun,MIPS,etc.) IDL data types.
COPY_STRUCT Copy all fields with matching tag names from one structure to another Fields with matching tag names are copied from one structure array to another structure array of different type. This allows copying of tag values when equating the structures of different types is not allowed, or when not all tags are to be copied. Can also recursively copy from/to structures nested within structures. Note that the number of elements in the output structure array is automatically adjusted to equal the length of input structure array. If this not desired then use pro copy_struct_inx which allows specifying via subscripts which elements are copied where in the arrays.
COPY_STRUCT_INX Copy matching tags & specified indices from one structure to another Copy all fields with matching tag names (except for "except_Tags") from one structure array to another structure array of different type. This allows copying of tag values when equating the structures of different types is not allowed, or when not all tags are to be copied. Can also recursively copy from/to structures nested within structures. This procedure is same as copy_struct with option to specify indices (subscripts) of which array elements to copy from/to.
CORREL_IMAGES Compute the 2-D cross-correlation function of two images Computes the 2-D cross-correlation function of two images for a range of (x,y) shifting by pixels of one image relative to the other.
CORREL_OPTIMIZE Find the optimal (x,y) pixel offset of image_B relative to image_A
CORRMAT_ANALYZE Find the optimal (x,y) offset to maximize correlation of 2 images Analyzes the 2-D cross-correlation function of two images and finds the optimal(x,y) pixel offsets. Intended for use with function CORREL_IMAGES.
COSMO_PARAM Derive full set of cosmological density parameters from a partial set This procedure is called by LUMDIST and GALAGE to allow the user a choice in defining any two of four cosmological density parameters.
CREATE_STRUCT Create an IDL structure from a list of tag names and dimensions Dynamically create an IDL structure variable from list of tag names and data types of arbitrary dimensions. Useful when the type of structure needed is not known until run time.
CR_REJECT General, iterative cosmic ray rejection using two or more input images. Uses a noise model input by the user, rather than determining noise empirically from the images themselves.
CSPLINE Function to evaluate a natural cubic spline at specified data points Combines the Numerical Recipes functions SPL_INIT and SPL_INTERP
CT2LST To convert from Local Civil Time to Local Mean Sidereal Time.
CURS Selects an X windows cursor shape
CURVAL Cursor controlled display of image intensities and astronomical coords CURVAL displays different information depending whether the user supplied an image array, and/or a FITS header array
DAOERF Calulates the intensity, and derivatives, of a 2-d Gaussian PSF Corrects for the finite size of a pixel by integrating the Gaussian over the size of the pixel. Used in the IDL-DAOPHOT sequence.
DAO_VALUE Returns the value of a DAOPHOT point-spread function at a set of points. The value of the point-spread function is the sum of a two-dimensional integral under a bivariate Gaussian function, and a value obtained by interpolation in a look-up table. DAO_VALUE will optionally compute the derivatives wrt X and Y
DATATYPE() Returns the data type of a variable. This routine returns the data type of a variable in a format specified by the optional flag parameter. Can also be used to emulate, in earlier versions of IDL, the SIZE(/TNAME) option introduced in V5.2.
DATE Convert day-of-year to a DD-MMM-YYYY string
DATE_CONV Procedure to perform conversion of dates to one of three possible formats. The following date formats are allowed
DAYCNV Converts Julian dates to Gregorian calendar dates
DBBUILD Build a database by appending new values for every item. The database must be opened for update (with DBOPEN) before calling
DBCIRCLE Find sources in a database within specified radius of specified center Database must include items named 'RA' (in hours) and 'DEC' (in degrees) and must have previously been opened with DBOPEN
DBCLOSE procedure to close a data base file
DBCOMPARE Display two entries in an IDL database side by side in a column format
DBCOMPRESS Compress a .dbf database file after a call to DBDELETE The procedure DBDELETE will remove specified entries from a database but it will not free the unused space. DBCOMPRESS will compress the .dbf file so that it only contains valid entries.
DBCREATE Create a new data base (.dbf), index (.dbx) or description (.dbh) file A database definition (.dbd) file must already exist. The default directory must be a ZDBASE: directory.
DBDELETE Deletes specified entries from data base
DBEDIT Interactively edit specified fields in a database. The value of each field is displayed, and the user has the option of changing or keeping the value. Widgets will be used if they are available.
DBEDIT_BASIC Subroutine of DBEDIT_BASIC to edit a database on a dumb terminal. Interactively edit specified fields in a database. The value of each field is displayed, and the user has the option of changing or keeping the value.
DBEXT Extract values of up to 12 items from an IDL database Procedure to extract values of up to 12 items from data base file, and place into IDL variables
DBEXT_DBF Subroutine of DBEXT to extract values of up to 18 items from a database This is a subroutine of DBEXT, which is the routine a user should
DBEXT_IND routine to read a indexed item values from index file
DBFIND() Search data base for entries with specified characteristics Function to search data base for entries with specified search characteristics.
DBFIND_ENTRY Subroutine of DBFIND to perform an entry number search This is a subroutine of dbfind and is not a standalone procedure It performs a entry number search.
DBFIND_SORT Subroutine of DBFIND to perform a search using sorted values This is a subroutine of dbfind and is not a standalone procedure It is used to limit the search using sorted values
DBFPARSE Parse the search string supplied to DBFIND. Not a standalone routine
DBGET Find entry numbers which contain specified values of a given item. DBGET() is useful as an alternative to DBFIND() when the desired search values are not easily expressed as a string.
DBHELP List available databases or items in the currently open database Procedure to either list available databases (if no database is currently open) or the items in the currently open database.
DBINDEX Procedure to create index file for data base
DBINDEX_BLK Subroutine of DBINDEX to create associated variable of correct datatype DBINDEX_BLK will offset into the file by a specified amount in preparation for writing to the file.
DBMATCH Find the entry number in a database for each element of item values DBMATCH() is especially useful for finding a one-to-one correspondence between entries in different databases, and thus to create the vector needed for database pointers.
DBOPEN Routine to open an IDL database
DBPRINT Procedure to print specified items from a list of database entries
DBPUT Procedure to place a new value for a specified item into a data base file entry.
DBRD procedure to read an entry from a data base file or from linked multiple databases.
DBSEARCH Subroutine of DBFIND() to search a vector for specified values
DBSORT Routine to sort list of entries in data base
DBTITLE function to create title line for routine dbprint
DBUPDATE Update columns of data in a database -- inverse of DBEXT Database must be open for update before calling DBUPDATE
DBVAL procedure to extract value(s) of the specified item from a data base file entry.
DBWRT procedure to update or add a new entry to a data base
DBXPUT routine to replace value of an item in a data base entry
DBXVAL Quickly return a value of the specified item number Procedure to quickly return a value of the specified item number from the entry.
DB_ENT2EXT Convert a database entry to external (IEEE) data format Converts a database entry to external (IEEE) data format prior to writing it. Called from DBWRT.
DB_ENT2HOST Converts a database entry from external data format to host format. All items are extracted from the entry, and then converted to host format, and placed back into the entry. Called from DBRD and DBEXT_DBF.
DB_INFO Function to obtain information on opened data base file(s)
DB_ITEM Returns the item numbers and other info. for an item name. Procedure to return the item numbers and other information of a specified item name
DB_ITEM_INFO routine to return information on selected item(s) in the opened
DB_OR Combine two vectors of entry numbers, removing duplicate values. DB_OR can also be used to remove duplicate values from any longword
DB_TITLES Print database name and title. Called by DBHELP
DEF_DIRLIST Define directory list using setenv or setlog Environment variables which point to a list of directories can end up to be very long. In VMS this can be a problem, because logical names cannot be longer than 256 characters. However, it is possible to get around this in VMS by assigning multiple values to a single logical name--a facility that does not exist in Unix.
DELVARX Delete variables for memory management (can call from routines) Like intrinsic DELVAR function, but can be used from any calling level
DEREDD Deredden stellar Stromgren parameters given for a value of E(b-y) See the procedure UVBYBETA for more info.
DETABIFY Replaces tabs in character strings with appropriate number of spaces The number of space characters inserted is calculated to space out to the next effective tab stop, each of which is eight characters
DISMOUNT Emulates the VMS DISMOUNT function in Unix. Emulates the VMS DISMOUNT function in the Unix environment. Although this is not a standard IDL function, it is available as a separate LINKIMAGE routine for VMS.
DIST_CIRCLE Form a square array where each value is its distance to a given center. Returns a square array in which the value of each element is its distance to a specified center. Useful for circular aperture photometry.
DIST_ELLIPSE Create a mask array useful for elliptical aperture photemetry Form an array in which the value of each element is equal to the semi-major axis of the ellipse of specified center, axial ratio, and position angle, which passes through that element. Useful for elliptical aperture photometry.
EQPOLE Convert RA and Dec to X,Y using an equal-area polar projection. The output X and Y coordinates are scaled to be between -90 and +90 to go from equator to pole to equator. Output map points can be centered on the north pole or south pole.
EQPOLE_GRID Produce an equal area polar projection grid overlay Grid is written on the current graphics device using the equal area polar projection. EQPOLE_GRID assumes that the output plot coordinates span the x and y ranges of -90 to 90 for a region that covers the equator to the chosen pole. The grid is assumed to go from the equator to the chosen pole.
EULER Transform between Galactic, celestial, and ecliptic coordinates. Use the procedure ASTRO to use this routine interactively
EXPAND_TILDE() Expand tilde in UNIX directory names
EXTAST Extract astrometry parameters from a FITS image header. The astrometry in the header can be in either CD (Coordinate description) format, or CROTA and CDELT (AIPS-type) format. However, the output astrometry will always be in CD format.
EXTGRP Extract the group parameter information out of SXREAD output This procedure extracts the group parameter information out of a header and parameter variable obtained from SXREAD. This allows astrometry, photometry and other parameters to be easily SXPARed by conventional methods and allows the image and header to be saved in a SIMPLE format.
EXTRAP This procedure fills in the ends of a one-dimensional array from interior portions using polynomial extrapolation.
FACTOR Find prime factors of a given number.
FDECOMP Routine to decompose a file name for any operating system
FILTER_IMAGE Identical to MEDIAN or SMOOTH but handle edges and allow iterations. Computes the average and/or median of pixels in moving box, replacing center pixel with the computed average and/or median, (using the IDL smooth or median functions). The main reason for using this function is the options to also process the pixels at edges and corners of image, and, to apply iterative smoothing simulating convolution with Gaussian, and/or to convolve image with a Gaussian kernel.
FIND Find positive brightness perturbations (i.e stars) in an image Also returns centroids and shape parameters (roundness & sharpness). Adapted from 1986 STSDAS version of DAOPHOT.
FINDPRO Find all locations of a procedure in the IDL !PATH FINDPRO searces for the procedure name (as a .pro or a .sav file) in all IDL libraries or directories given in the !PATH system variable.
FIND_ALL_DIR() Finds all directories under a specified directory. This routine finds all the directories in a directory tree when the root of the tree is specified. This provides the same functionality as having a directory with a plus in front of it in the environment variable IDL_PATH.
FIND_WITH_DEF() Searches for files with a default path and extension. Finds files using default paths and extensions, similar to using the DEFAULT keyword with the OPEN statement in VMS. Using this routine together with environment variables allows an OS-independent approach to finding files.
FITEXY Best straight-line fit to data with errors in both coordinates Linear Least-squares approximation in one-dimension (y = a + b*x), when both x and y data have errors
FITSDIR Provide a brief description of the primary headers of FITS disk files. The values of the FITS keywords NAXISi, OBS-DATE (or TDATEOBS or DATE), TELESCOPE (or INSTRUME), OBJECT (or TARGNAME), EXPTIME (or INTEG) are displayed. All of these are commonly used FITS keywords and all except EXPTIME are officially reserved FITS keywords. Keyword names in parentheses are searched if the primary keyword is not
FITSLIST Display and write FITS headers from a FITS tape Procedure will read FITS files from a tape on the specified tape unit. The headers are placed in file NAME, with the default extension of .LIS. Headers are also displayed at the terminal. Unix and VMS IDL only.
FITSRGB_TO_TIFF Combine separate red, green, and blue FITS images into TIFF format The output TIFF (class R) file can have colors interleaved either either by pixel or image. The colour mix is also adjustable.
FITSTAPE Subroutine to perform FITS tape I/O. For VMS or Unix IDL only
FITS_CD_FIX Convert between different representations of the CD matrix in a FITS header According the paper, "Representations of Celestial Coordinates in FITS" by Griesen and Calabretta, available at http://www.cv.nrao.edu/fits/documents/wcs/wcs.html the rotation of an image from standard coordinates is represented by a coordinate description (CD) matrix. However, there have been several different representations proposed for the CD matrix. Currently, (April 2000), the preferred form is CDn_m (as used in IRAF), which contains both rotation & plate scale info. However, an earlier draft of Griesen & Calabretta proposed the CD00n00m form.
FITS_CLOSE Close a FITS data file
FITS_HELP To print a summary of the primary data units and extensions in a
FITS_INFO Provide information about the contents of a FITS file Information includes number of header records and size of data array. Applies to primary header and all extensions. Information can be printed at the terminal and/or stored in a common block
FITS_OPEN Opens a FITS (Flexible Image Transport System) data file.
FITS_READ To read a FITS file.
FITS_WRITE To write a FITS primary data unit or extension.
FLEGENDRE Compute the first M terms in a Legendre polynomial expansion. Meant to be used as a supplied function to SVDFIT.
FLUX2MAG Convert from flux (ergs/s/cm^2/A) to magnitudes. Use MAG2FLUX() for the opposite direction.
FM_UNRED Deredden a flux vector using the Fitzpatrick (1999) parameterization The R-dependent Galactic extinction curve is that of Fitzpatrick & Massa (Fitzpatrick, 1999, PASP, 111, 63; astro-ph/9809387 ). Parameterization is valid from the IR to the far-UV (3.5 microns to 0.1 microns). UV extinction curve is extrapolated down to 912 Angstroms.
FORPRINT Print a set of vectors by looping over each index value. If W and F are equal length vectors, then the statement IDL> forprint, w, f is equivalent to IDL> for i = 0L, N_elements(w)-1 do print,w[i],f[i]
FREBIN Shrink or expand the size of an array an arbitary amount using interpolation FREBIN is an alternative to CONGRID or REBIN. Like CONGRID it allows expansion or contraction by an arbitary amount. ( REBIN requires integral factors of the original image size.) Like REBIN it conserves flux by ensuring that each input pixel is equally represented in the output
FSTRING Shell around STRING function to fix 1024 size limit on formatting strings
FTAB_DELROW Delete rows of data from a FITS ASCII or binary table extension
FTAB_EXT Routine to extract columns from a FITS (binary or ASCII) table
FTAB_HELP Describe the columns of a FITS binary or ASCII table extension.
FTAB_PRINT Print the contents of a FITS (binary or ASCII) table extension. User can specify which rows or columns to print
FTADDCOL Routine to add a field to a FITS ASCII table
FTCREATE Create a new (blank) FITS ASCII table and header with specified size.
FTDELCOL Delete a column of data from a FITS table
FTDELROW Delete a row of data from a FITS table
FTGET Function to return value(s) from specified column in a FITS ASCII table
FTHELP Routine to print a description of a FITS ASCII table extension
FTHMOD Procedure to modify header information for a specified field in a FITS table.
FTINFO Return an informational structure from a FITS ASCII table header.
FTKEEPROW Subscripts (and reorders) a FITS table. A companion piece to FTDELROW.
FTPRINT Procedure to print specified columns and rows of a FITS table
FTPUT Procedure to add or update a field in an FITS ASCII table
FTSIZE Procedure to return the size of a FITS ASCII table.
FTSORT Sort a FITS ASCII table according to a specified field
FXADDPAR Add or modify a parameter in a FITS header array. This version of FXADDPAR will write string values longer than 68 characters using the FITS continuation convention described at http://heasarc.gsfc.nasa.gov/docs/heasarc/ofwg/docs/ofwg_recomm/r13.html
FXBADDCOL Adds a column to a binary table extension. Modify a basic FITS binary table extension (BINTABLE) header array to define a column.
FXBCLOSE Close a FITS binary table extension opened for read. Closes a FITS binary table extension that had been opened for read by
FXBCOLNUM Returns a binary table column number. Given a column specified either by number or name, this routine will return the appropriate column number.
FXBCREATE Open a new binary table at the end of a FITS file. Write a binary table extension header to the end of a disk FITS file, and leave it open to receive the data.
FXBDIMEN Project : SOHO - CDS Name : FXBDIMEN() Purpose : Returns the dimensions for a column in a FITS binary table. Explanation : This procedure returns the dimensions associated with a column in a binary table opened for read with the command FXBOPEN. Use : Result = FXBDIMEN(UNIT,COL)
FXBFIND Find column keywords in a FITS binary table header. Finds the value of a column keyword for all the columns in the binary table for which it is set. For example,
FXBFINDLUN Find logical unit number UNIT in FXBINTABLE common block. Finds the proper index to use for getting information about the logical unit number UNIT in the arrays stored in the FXBINTABLE common block. Called from FXBCREATE and FXBOPEN.
FXBFINISH Close a FITS binary table extension file opened for write. Closes a FITS binary table extension file that had been opened for write by FXBCREATE.
FXBGROW Increase the number of rows in a binary table. Call FXBGROW to increase the size of an already-existing FITS binary table. The number of rows increases to NROWS (or does not change if NROWS is less than the number of rows already existing). WARNING: the table to be grown must be the *last* extension in the FITS file. FXBGROW does *not* preserve any following extensions. This procedure is useful when a table with an unknown number of rows must be created. The caller would then call FXBCREATE to construct a table of some base size, and follow with calls to FXBGROW to lengthen the table
FXBHEADER Project : SOHO - CDS Name : FXBHEADER() Purpose : Returns the header of an open FITS binary table. Explanation : This procedure returns the FITS extension header of a FITS binary table opened for read with the command FXBOPEN. Use : Result = FXBHEADER(UNIT)
FXBHELP Prints short description of columns in a FITS binary table. Prints a short description of the columns in a FITS binary table to the terminal screen.
FXBHMAKE Create basic FITS binary table extension (BINTABLE) header. Creates a basic header array with all the required keywords, but with none of the table columns defined. This defines a basic structure which can then be added to or modified by other routines.
FXBINTABLE Common block FXBINTABLE used by "FXB" routines. This is not an IDL routine as such, but contains the definition of the common block FXBINTABLE for inclusion into other routines. By defining the common block in one place, the problem of conflicting definitions
FXBISOPEN Project : SOHO - CDS Name : FXBISOPEN() Purpose : Returns true if UNIT points to an open FITS binary table. Explanation : This procedure checks to see if the logical unit number given by the variable UNIT corresponds to a FITS binary table opened for read with the command FXBOPEN, and which has not yet been
FXBOPEN Open binary table extension in a disk FITS file for reading. Opens a binary table extension in a disk FITS file for reading. The columns are then read using FXBREAD, and the file is closed when done with FXBCLOSE.
FXBPARSE Parse the binary table extension header. Parses the binary table extension header, and store the information about the format of the binary table in the FXBINTABLE common block--called from FXBCREATE and FXBOPEN.
FXBREAD Read a data array from a disk FITS binary table file. Each call to FXBREAD will read the data from one column and one row from the FITS data file, which should already have been opened by FXBOPEN. One needs to call this routine for every column and every row in the binary table. FXBCLOSE will then close the FITS data file.
FXBREADM Read multiple columns/rows from a disk FITS binary table file. A call to FXBREADM will read data from multiple rows and multiple columns in a single procedure call. Up to fifty columns may be read in a single pass; the number of rows is limited essentially by available memory. The file should have already been opened with FXBOPEN. FXBREADM optimizes reading multiple columns by first reading a large chunk of data from the FITS file directly, and then slicing the data into columns within memory. FXBREADM cannot read variable-length arrays; use FXBREAD instead.
FXBSTATE Project : SOHO - CDS Name : FXBSTATE() Purpose : Returns the state of a FITS binary table. Explanation : This procedure returns the state of a FITS binary table that was either opened for read with the command FXBOPEN, or for write with the command FXBCREATE.
FXBTDIM Parse TDIM-like kwywords. Parses the value of a TDIM-like keyword (e.g. TDIMnnn, TDESC, etc.) to return the separate elements contained within.
FXBTFORM Returns information about FITS binary table columns. Procedure to return information about the format of the various columns in a FITS binary table.
FXBWRITE Write a binary data array to a disk FITS binary table file. Each call to FXBWRITE will write to the data file, which should already have been created and opened by FXBCREATE. One needs to call this routine for every column and every row in the binary table. FXBFINISH will then close the file.
FXBWRITM Write multiple columns/rows to a disk FITS binary table file. A call to FXBWRITM will write multiple rows and multiple columns to a binary table in a single procedure call. Up to fifty columns may be read in a single pass. The file should have already been opened with FXBOPEN (with write access) or FXBCREATE. FXBWRITM optimizes writing multiple columns by first writing a large chunk of data to the FITS file all at once. FXBWRITM cannot write variable-length arrays; use FXBWRITE instead.
FXFINDEND Find the end of a FITS file. This routine finds the end of the last logical record in a FITS file, which may be different from that of the physical end of the file. Each FITS header is read in and parsed, and the file pointer is moved to where the next FITS extension header would be if there is one, or to the end of the file if not.
FXHCLEAN Removes required keywords from FITS header. Removes any keywords relevant to array structure from a FITS header, preparatory to recreating it with the proper values.
FXHMAKE Create a basic FITS header array. Creates a basic header array with all the required keywords. This defines a basic structure which can then be added to or modified by other routines.
FXHMODIFY Modify a FITS header in a file on disk. Opens a FITS file, and adds or modifies a parameter in the FITS header. Can be used for either the main header, or for an extension header. The modification is performed directly on the disk file.
FXHREAD Reads a FITS header from an opened disk file. Reads a FITS header from an opened disk file.
FXMOVE Skip a specified number of extensions in a FITS file
FXPAR() Obtain the value of a parameter in a FITS header. The first 8 chacters of each element of HDR are searched for a match to NAME. If the keyword is one of those allowed to take multiple values ("HISTORY", "COMMENT", or " " (blank)), then the value is taken as the next 72 characters. Otherwise, it is assumed that the next character is "=", and the value (and optional comment) is then parsed from the last 71 characters. An error occurs if there is no parameter with the given name.
FXPARPOS Finds position to insert record into FITS header. Finds the position to insert a record into a FITS header. Called from
FXPOSIT Return the unit number of a FITS file positioned at specified extension The FITS file will be ready to be read at the beginning of the specified extension.
FXREAD Read basic FITS files. Read the primary array from a disk FITS file. Optionally allows the user to read in only a subarray and/or every Nth pixel.
FXTAPEREAD Project : SOHO - CDS Name : FXTAPEREAD Purpose : Copy FITS files tape to disk with interactive capabilities. Explanation : Copy FITS files from tape onto disk. Data is left in FITS format, and not converted to SDAS. For use on VMS (any version) and UNIX running IDL Version 3.1 or later (see
FXTAPEWRITE Project : SOHO - CDS Name : FXTAPEWRITE Purpose : Procedure to copy disk FITS files to tape with interactive capabilities. Explanation : Writes the FITS files to tape based upon the parameters inputted or supplied. If no parameters are supplied, then the
FXTPIO_READ Copies FITS files from tape to disk -- internal routine. Procedure to copy a FITS file from a tape on the specified tape unit to the disk file .FITS (unless the /NOSUFFIX keyword has been set). For use on VMS (any version) and UNIX running IDL Version 3.1 or later (see Restrictions).
FXTPIO_WRITE Copy FITS files from disk to tape -- internal routine. Procedure will copy a disk FITS file to the specified tape unit, at the current tape position. Used for true disk FITS files, not SDAS/Geis files. Called by FXTAPEWRITE.
FXWRITE Write a disk FITS file. Creates a disk FITS file and writes a FITS primary header, and optionally a primary data array.
F_FORMAT Choose a nice floating format for displaying an array of REAL data. Called by TVLIST, IMLIST.
GALAGE Determine the age of a galaxy given its redshift and a formation redshift.
GAL_FLAT Transforms the image of a galaxy so that the galaxy appears face-on Either a nearest-neighbor approximations or a bilinear interpolation
GAUSSIAN Compute the 1-d Gaussian function and optionally the derivative Compute the 1-D Gaussian function and optionally the derivative at an array of points.
GCIRC Computes rigorous great circle arc distances. Input/Output can either be either sexigesimal RA, Dec, or in radians. All computations are double precision.
GETFILES Prompt the user to interactively specify a list of files User can specify a single file per line or a range of files separated by a dash or comma. Used, for example, by FITSRD to return a list of file numbers on tape to read
GETLOG Formats a logical directory for the given operating system.
GETOPT Convert a string supplied by the user into a valid scalar or vector Distinct elements in the string may be separated by either a comma or a space. The output scalar or vector can be specified to be either integer or floating point. A null string is converted to a zero. !ERR is set to the number of elements supplied.
GETPRO Search !PATH for a procedure, and copy into user's working directory Extract a procedure from an IDL Library or directory given in the !PATH system variable and place it in the current default directory (presumably to be edited by the user). GETPRO can also be used to obtain a copy of the default startup file.
GETPSF To generate a point-spread function (PSF) from observed stars. The PSF is represented as a 2-dimensional Gaussian (integrated over each pixel) and a lookup table of residuals. The lookup table and Gaussian parameters are output in a FITS image file. The PSF FITS file created by GETPSF can be read with the procedure RDPSF. Adapted from the 1986 STSDAS version of DAOPHOT
GETROT Return the rotation and plate scale of an image from its FITS header Derive the counterclockwise rotation angle, and the X and Y scale factors of an image, from a FITS image header. Input parameter may be either a FITS image header or an astrometry structure (as obtained by EXTAST.PRO)
GETTOK Retrieve the first part of the string up to a specified character GET TOKen - Retrieve first part of string until the character char is encountered.
GETWRD Return the n'th word from a text string.
GET_COORDS Converts a string with angular coordinates to floating point values. Although called by ASTRO.PRO, this is a general purpose routine. The user may input as floating point or sexigesimal. If user inputs calling procedure's job to convert hours to degrees if needed. Since the input string is parsed character-by-character, ANY character that is not a digit, minus sign or decimal point may be used as a delimiter, i.e. acceptable examples of user input are:
GET_DATE Return the current UTC date in CCYY-MM-DD format for FITS headers This is the format required by the DATE and DATE-OBS keywords in a
GET_EQUINOX Return the equinox value from a FITS header. Checks for 3 possibilities:
GET_JULDATE Return the current Julian Date This procedure became partially obsolete with the introduction of the /JULIAN keyword to the intrinsic SYSTIME function in IDL V5.2. Note however, that SYSTIME(/JULIAN) always returns the *local* time, whereas for most machines, GET_JULDATE returns Universal Time (i.e. Greenwich
GLACTC Convert between celestial and Galactic coordinates. Program to convert right ascension (ra) and declination (dec) to Galactic longitude (gl) and latitude (gb) (j=1) or vice versa (j=2).
GROUP Assign stars with non-overlapping PSF profiles into distinct groups Part of the IDL-DAOPHOT sequence
GSSSADXY Converts RA and DEC (J2000) to (X,Y) for an STScI GuideStar image. The sky coordinates may be printed and/or returned in variables.
GSSSEXTAST Extract IDL astrometry structure from a ST Guide Star Survey FITS header This procedure extracts the astrometry information from a ST Guide Star Survey FITS header and places it in an IDL structure for subsequent use with GSSSxyad and GSSSadxy.
GSSSXYAD Convert (X,Y) coordinates in a STScI Guide Star image to RA and Dec The sky coordinates may be printed and/or returned in variables.
GSSS_STDAST Insert the closest tangent projection astrometry into an GSSS Image This procedure takes a header with GSSS (ST Guide Star Survey) astrometry and writes a roughly equivalent tangent projection astrometry into the header.
HASTROM Linear transformation of an image to align it with a reference image A linear transformation is applied (using POLY_2D) to an image so that its astrometry is identical with that in a reference header. This procedure can be used to align two images.
HBOXAVE Box average an image array and update the FITS header array The function BOXAVE() is used. This procedure is recommended for integer images when photometric precision is desired, because it performs intermediate steps using REAL*4 arithmetic. Otherwise, the procedure HREBIN is much faster.
HCONGRID CONGRID an image and update astrometry in a FITS header Expand or contract an image using CONGRID and update the associated FITS header array.
HEADFITS Read a FITS (primary or extension) header into a string array. Under Unix, HEADFITS() can also read gzip (.gz) or Unix compressed (.Z) FITS files. In IDL V5.3 or later, HEADFITS() can read gzip files under any machine OS.
HELIO Compute (low-precision) heliocentric coordinates for the planets. The mean orbital elements for epoch J2000 are used. These are derived from a 250 yr least squares fit of the DE 200 planetary ephemeris to a Keplerian orbit where each element is allowed to vary linearly with time. For dates between 1800 and 2050, this solution fits the terrestrial planet orbits to ~25" or better, but achieves only ~600"
HELIO_JD Convert geocentric (reduced) Julian date to heliocentric Julian date This procedure corrects for the extra light travel time between the Earth and the Sun.
HELIO_RV Return the heliocentric radial velocity of a spectroscopic binary This function will return the heliocentric radial velocity of a spectroscopic binary star at a given heliocentric Julian date (HJD) given its orbit.
HERMITE To compute Hermite spline interpolation of a tabulated function. Hermite interpolation computes the cubic polynomial that agrees with the tabulated function and its derivative at the two nearest tabulated points. It may be preferable to Lagrangian interpolation (QUADTERP) when either (1) the first derivatives are known, or (2) one desires continuity of the first derivative of the interpolated values. HERMITE() will numerically compute the necessary derivatives, if they are not supplied.
HEXTRACT Extract a subimage from an array and update astrometry in FITS header Extract a subimage from an array and create a new FITS header with updated astrometry for the subarray
HGREP Find a substring in a FITS header (or any other string array)
HOST_TO_IEEE Translate an IDL variable from host to IEEE representation The variable is converted from the format used by the host architecture into IEEE-754 representation (as used, for example, in FITS data ).
HPRECESS Precess the astrometry in a FITS header to a new equinox
HPRINT Print a FITS header (or other string array) one line at a time The string array is printed 1 line at a time. Needed because IDL will add an extra space to the 80 character FITS lines on TTY terminals, causing a space to appear betweeen lines.
HREBIN Expand or contract a FITS image using (F)REBIN and update the header If output size is a multiple of input size then REBIN is used, else FREBIN is used. User can either overwrite the input array, or write to new variables.
HREVERSE Reverse an image about either dimension and update FITS astrometry Reverse an image about either the X or Y axis, and create a new header with updated astrometry for the reversed image.
HROT Rotate an image and create new FITS header with updated astrometry. Cubic, bilinear or nearest neighbor interpolation can be used.
HROTATE Apply the IDL ROTATE function and update astrometry in a FITS header Apply the intrinsic IDL ROTATE function to an image and update astrometry in the associated FITS header.
IEEE_TO_HOST Translate an IDL variable from IEEE-754 to host representation The variable is translated from IEEE-754 (as used, for example, in FITS data ), into the host machine architecture.
IMCONTOUR Make a contour plot labeled with astronomical coordinates. The type of coordinate display is controlled by the keyword TYPE Set TYPE=0 (default) to measure distances from the center of the image (IMCONTOUR will decide whether the plotting units will be in arc seconds, arc minutes, or degrees depending on image size.) Set /TYPE for standard RA and Dec labeling
IMDBASE Find the sources in an IDL database that are located on a given image.
IMF Compute an N-component power-law logarithmic initial mass function
IMGREAD Read a WFPC or FOC file into IDL image and data arrays Open an SDAS/GEIS file and read the image into a data array of appropriate type and read the header into a string array. This procedure was designed to be more versatile than the STRD procedure and to be specifically useful to WF/PC and FOC data, as well as all other GEIS images. IMGread supports multiple GROUPS (i.e. in STSDAS
IMLIST Display pixel values on an image surrounding a specified X,Y center. IMLIST is similar to TVLIST but the center pixel is supplied directly by the user, rather than being read off of the image display
IRAFDIR Provide a brief description of the IRAF images on a directory
IRAFRD Read an IRAF (.imh) file into IDL image and header arrays. The internal IRAF format changed somewhat in IRAF V2.11 to a machine independent format, with longer filename allocations. This version of IRAFRD should be able to read either format.
IRAFWRT Write IDL data in IRAF (OIF) format (.imh and .pix files). Does the reverse of IRAFRD. IRAFWRT writes the "old" IRAF format used prior to v2.11. However, this "old" format is still readable by the current version of IRAF.
ISARRAY Tests if the argument is an array.
ISMEUV Compute the interstellar EUV optical depth The EUV optical depth is computed from the photoionization of hydrogen and helium.
IS_IEEE_BIG Determine if the current machine is use IEEE, big-endian numbers. (Big endian implies that byteorder XDR conversions are no-ops).
JDCNV Converts Gregorian dates to Julian days
JPRECESS Precess astronomical coordinates from B1950 to J2000 Calculate the mean place of a star at J2000.0 on the FK5 system from the mean place at B1950.0 on the FK4 system.
JULDATE Convert from calendar to Reduced Julian Date Julian Day Number is a count of days elapsed since Greenwich mean noon on 1 January 4713 B.C. The Julian Date is the Julian day number followed by the fraction of the day elapsed since the preceding noon.
KSONE Compute the one-sided Kolmogorov-Smirnov statistic Returns the Kolmogorov-Smirnov statistic and associated probability for for an array of data values and a user-supplied cumulative distribution function (CDF) of a single variable. Algorithm from the procedure of the same name in "Numerical Recipes" by Press et al. 2nd edition (1992)
KSTWO Return the two-sided Kolmogorov-Smirnov statistic Returns the Kolmogorov-Smirnov statistic and associated probability that two arrays of data values are drawn from the same distribution Algorithm taken from procedure of the same name in "Numerical Recipes" by Press et al., 2nd edition (1992), Chapter 14
LEGEND Create an annotation legend for a plot. This procedure makes a legend for a plot. The legend can contain a mixture of symbols, linestyles, Hershey characters (vectorfont), and filled polygons (usersym). A test procedure, legendtest.pro, shows legend's capabilities. Placement of the legend is controlled with keywords like /right, /top, and /center or by using a position keyword for exact placement (position=[x,y]) or via mouse (/position).
LEGENDTEST Demo program to show capabilities of the legend procedure.
LINEID_PLOT Plot spectrum with specified line identifications annotated at the top of the plot.
LINTERP Linearly interpolate tabulated 1-d data from one grid to a new one. The results of LINTERP are numerically equivalent to the RSI INTERPOL() function, but note the followign: (1) LINTERP is a procedure rather than a function (2) INTERPOL() extrapolates beyond the end points whereas LINTERP truncates to the endpoints (or use the MISSING keyword) (3) LINTERP (unlike INTERPOL) uses the intrinsic INTERPOLATE function and thus may have a speed advantage
LIST_WITH_PATH Search for files in a specified directory path. Lists files in a set of default paths, similar to using FINDFILE, except that a list of paths to be searched can be given.
LUMDIST Calculate luminosity distance (in Mpc) of an object given its redshift The luminosity distance in the Friedmann-Robertson-Walker model is taken from Caroll, Press, and Turner (1992, ARAA, 30, 499), p. 511 Uses a closed form (Mattig equation) to compute the distance when the cosmological constant is zero. Otherwise integrates the function using
MAG2FLUX Convert from magnitudes to flux (ergs/s/cm^2/A). Use FLUX2MAG() for the opposite direction.
MAKE_2D Change from 1-d indexing to 2-d indexing Convert an N element X vector, and an M element Y vector, into N x M arrays giving all possible combination of X and Y pairs. Useful for obtaining the X and Y positions of each element of a regular grid.
MAKE_ASTR Build an astrometry structure from input parameter values This structure can be subsequently placed in a FITS header with
MATCH Routine to match values in two vectors.
MAX_ENTROPY Deconvolution of data by Maximum Entropy analysis, given the PSF Deconvolution of data by Maximum Entropy analysis, given the instrument point spread response function (spatially invariant psf). Data can be an observed image or spectrum, result is always positive. Default is convolutions using FFT (faster when image size = power of 2).
MAX_LIKELIHOOD Maximum likelihood deconvolution of an image or a spectrum. Deconvolution of an observed image (or spectrum) given the instrument point spread response function (spatially invariant psf). Performs iteration based on the Maximum Likelihood solution for the restoration of a blurred image (or spectrum) with additive noise. Maximum Likelihood formulation can assume Poisson noise statistics or Gaussian additive noise, yielding two types of iteration.
MEANCLIP Computes an iteratively sigma-clipped mean on a data set Clipping is done about median, but mean is returned. Called by SKYADJ_CUBE
MEDARR Compute the median at each pixel across a set of 2-d images Each pixel in the output array contains the median of the corresponding pixels in the input arrays. Useful, for example to combine a stack of CCD images, while removing cosmic ray hits.
MID_RD_DISDSC Get a MIDAS directory descriptor from a MIDAS BDF. Note: PORTABLE MIDAS.
MID_RD_IMAGE Get a pixel matrix and some support information from a MIDAS file.
MID_RD_TABLE Open and read data from a MIDAS table.
MID_UP_IMAGE Get a pixel matrix and some support information from a MIDAS file. Allows updating of data, using DATA parameter.
MID_UP_TABLE Open and update data from a MIDAS table.
MINF_BRACKET Bracket a local minimum of a 1-D function with 3 points, Brackets a local minimum of a 1-d function with 3 points, thus ensuring that a minimum exists somewhere in the interval. This routine assumes that the function has a minimum somewhere.... Routine can also be applied to a scalar function of many variables, for such case the local minimum in a specified direction is bracketed, This routine is called by minF_conj_grad, to bracket minimum in the direction of the conjugate gradient of function of many variables CALLING EXAMPLE:
MINF_CONJ_GRAD Find the local minimum of a scalar function using conjugate gradient Find the local minimum of a scalar function of several variables using the Conjugate Gradient method (Fletcher-Reeves-Polak-Ribiere algorithm). Function may be anything with computable partial derivatives. Each call to minF_conj_grad performs one iteration of algorithm, and returns an N-dim point closer to the local minimum of function. CALLING EXAMPLE: p_min = replicate( 1, N_dim ) minF_conj_grad, p_min, f_min, conv_factor, FUNC_NAME="name",/INITIALIZE
MINF_PARABOLIC Minimize a function using Brent's method with parabolic interpolation Find a local minimum of a 1-D function up to specified tolerance. This routine assumes that the function has a minimum nearby. (recommend first calling minF_bracket, xa,xb,xc, to bracket minimum). Routine can also be applied to a scalar function of many variables, for such case the local minimum in a specified direction is found, This routine is called by minF_conj_grad, to locate minimum in the direction of the conjugate gradient of function of many variables.
MINF_PARABOL_D Minimize a function using a modified Brent's method with derivatives Based on the procedure DBRENT in Numerical Recipes by Press et al. Finds a local minimum of a 1-D function up to specified tolerance, using the first derivative of function in the algorithm. This routine assumes that the function has a minimum nearby. (recommend first calling minF_bracket, xa,xb,xc, to bracket minimum). Routine can also be applied to a scalar function of many variables, for such case the local minimum in a specified direction is found, This routine is called by minF_conj_grad, to locate minimum in the direction of the conjugate gradient of function of many variables.
MINMAX Return a 2 element array giving the minimum and maximum of an array Using MINMAX() is faster than doing a separate MAX and MIN.
MKHDR Make a minimal primary (or IMAGE extension) FITS header If an array is supplied, then the created FITS header will be appropriate to the supplied array. Otherwise, the user can specify the dimensions and datatype.
MMM Estimate the sky background in a stellar contaminated field. MMM assumes that contaminated sky pixel values overwhelmingly display POSITIVE departures from the true value. Adapted from DAOPHOT routine of the same name.
MODFITS Modify a FITS file by updating the header and/or data array. The updated header or array cannot change the size of the FITS file.
MONTH_CNV This function will convert a month name to the equivalent number (e.g., January --> 1) or vice-versa.
MOONPOS To compute the RA and Dec of the Moon at specified Julian date(s).
MPHASE Return the illuminated fraction of the Moon at given Julian date(s)
MRDFITS Read all standard FITS data types into arrays or structures. Further information on MRDFITS is available at http://idlastro.gsfc.nasa.gov/mrdfits.html
MRD_HREAD Reads a FITS header from an opened disk file or Unix pipe Like FXHREAD but also works with compressed Unix files
MRD_SKIP Skip a number of bytes from the current location in a file or a pipe First tries using POINT_LUN and if this doesn't work, perhaps because the unit is a pipe, MRD_SKIP will just read in the requisite number
MRD_STRUCT Return a structure as defined in the names and values data.
MULTIPLOT Create multiple plots with shared axes. This procedure makes a matrix of plots with *SHARED AXES*, either using parameters passed to multiplot or !p.multi in a non-standard way. It is good for data with one or two shared axes and retains all the versatility of the plot commands (e.g. all keywords and log scaling). The plots are connected with the shared axes, which saves space by omitting redundant ticklabels and titles. Multiplot does this by setting !p.position, !x.tickname and !y.tickname automatically. A call (multiplot,/reset) restores original values.
MWRFITS Write all standard FITS data types from input arrays or structures.
NGP Interpolate an irregularly sampled field using Nearest Grid Point This function interpolates irregularly gridded points to a regular grid using Nearest Grid Point.
NINT Nearest integer function. NINT() is similar to the intrinsic ROUND function, with the following two differences: (1) if no absolute value exceeds 32767, then the array is returned as as a type INTEGER instead of LONG (2) NINT will work on strings, e.g. print,nint(['3.4','-0.9']) will
NSTAR Simultaneous point spread function fitting (adapted from DAOPHOT)
NULLTRIM Trim a string of all characters after and including the first null The null character is an ascii 0b
NUMLINES() Return the number of lines in a file
NUTATE Return the nutation in longitude and obliquity for a given Julian date
N_STRUCT To determine if variable is a structure and return number of elements.
OBSERVATORY Return longitude, latitude, altitude & time zones of an observatory Given an observatory name, returns a structure giving the longitude, latitude, altitude, and time zone
ONE_ARROW Draws an arrow labeled with a single character on the current device ONE_ARROW is called, for example, by ARROWS to create a "weathervane" showing the N-E orientation of an image.
ONE_RAY Draw a line with a specified starting point, length, and angle
OPLOTERROR Over-plot data points with accompanying X or Y error bars. For use instead of PLOTERROR when the plotting system has already been
ORDINAL Convert an integer to a correct English ordinal string: The first four ordinal strings are "1st", "2nd", "3rd", "4th" ....
OSFCNVRT Return the correctly formatted logical directory syntax for the host OS
PARTVELVEC Plot the velocity vectors of particles at their positions This procedure plots the velocity vectors of particles (at the positions of the particles).
PCA Carry out a Principal Components Analysis (Karhunen-Loeve Transform) Results can be directed to the screen, a file, or output variables See notes below for comparison with the intrinisc IDL function PCOMP.
PENT Return the information entropy of a time series This function will return S, the information entropy of a time series for a set of trial periods
PIXCOLOR Assign colors to specified pixel values in a color lookup table
PIXWT Circle-rectangle overlap area computation. Compute the fraction of a unit pixel that is interior to a circle. The circle has a radius r and is centered at (xc, yc). The center of the unit pixel (length of sides = 1) is at (x, y).
PKFIT Subroutine of GETPSF to perform a one-star least-squares fit Part of the DAOPHOT PSF photometry sequence
PLANCK() To calculate the Planck function in units of ergs/cm2/s/A
PLANET_COORDS Find low-precision RA and DEC for the planets given a date This routine uses HELIO to get the heliocentric ecliptic coordinates of the planets at the given date, then converts these to geocentric ecliptic coordinates ala "Astronomical Alogrithms" by Jean Meeus (1991, p 209). These are then converted to RA and Dec using EULER. The accuracy between the years 1800 and 2050 is better than 1 arcminute for the terrestial planets, but reaches 10 arcminutes for Saturn. Before 1850 or after 2050 the accuracy can get much worse.
PLOTERROR Plot data points with accompanying X or Y error bars. This is a greatly enhanced version of the standard IDL Library routine
PLOTHIST Plot the histogram of an array with the corresponding abcissa.
PLOTSYM Define useful plotting symbols not in the standard !PSYM definitions. After a symbol has been defined with PLOTSYM, a plotting command should follow with either PSYM = 8 or !P.PSYM = 8 (see USERSYM)
POIDEV Generate a Poisson random deviate Return an integer random deviate drawn from a Poisson distribution with a specified mean. Adapted from procedure of the same name in "Numerical Recipes" by Press et al. (1992), Section 7.3
POLINT Interpolate a set of N points by fitting a polynomial of degree N-1 Adapted from algorithm in Numerical Recipes, Press et al. (1992),
POLREC Convert 2-d polar coordinates to rectangular coordinates.
POLYLEG Evaluate a Legendre polynomial with specified coefficients. Meant to be used analogously to the POLY function in the IDL User's Library distribution.
POLY_SMOOTH Apply a least-squares (Savitzky-Golay) polynomial smoothing filter Reduce noise in 1-D data (e.g. time-series, spectrum) but retain dynamic range of variations in the data by applying a least squares smoothing polynomial filter,
POSANG Computes rigorous position angle of source 2 relative to source 1 Computes the rigorous position angle of source 2 (with given RA, Dec) using source 1 (with given RA, Dec) as the center.
POSITIVITY Map an image uniquely and smoothly into all positive values. Take unconstrained x (usually an image), and map it uniquely and smoothly into positive values. Negative values of x get mapped to interval ( 0, sqrt( epsilon )/2 ], positive values go to ( sqrt( epsilon )/2, oo ) with deriv approaching 1. Derivative is always 1/2 at x=0. Derivative is used by the MRL deconvolution
PRECESS Precess coordinates from EQUINOX1 to EQUINOX2. For interactive display, one can use the procedure ASTRO which calls PRECESS or use the /PRINT keyword. The default (RA,DEC) system is FK5 based on epoch J2000.0 but FK4 based on B1950.0 is available via the /FK4 keyword.
PRECESS_CD Precess the CD (coordinate description) matrix from a FITS header The CD matrix is precessed from EPOCH1 to EPOCH2. Called by HPRECESS
PRECESS_XYZ Precess equatorial geocentric rectangular coordinates.
PREMAT Return the precession matrix needed to go from EQUINOX1 to EQUINOX2.
PRIME Return an array with the specified number of prime numbers. EXPLANATATION: This procedure is similar to PRIMES in the standard IDL distribution, but stores results in a common block, and so is much faster
PRINT_STRUCT Print the tag values of an array of structures in nice column format. The tag names are displayed in a header line.
PROB_KS Return the significance of the Kolmogoroff-Smirnov statistic Returns the significance level of an observed value of the Kolmogorov-Smirnov statistic D for an effective number of data points N_eff. Called by KSONE and KSTWO
PRODUCT Calculates the product of all the elements of an array PRODUCT() is the multiplicative equivalent of TOTAL().
PSF_GAUSSIAN Create a 1-d, 2-d, or 3-d Gaussian with specified FWHM, center Return a point spread function having Gaussian profiles, as either a 1D vector, a 2D image, or 3D volumetric-data.
PUTAST Put astrometry parameters into a given FITS header.
QDCB_GRID Produce an overlay of latitude and longitude lines over a plot or image Grid is plotted on the current graphics device assuming that the current plot is a map in the so called quad cube projection. The output plot range is assumed to go from 7.0 to -1.0 on the X axis and -3.0 to 3.0 on the Y axis. Within this plotting space, the quad cube faces are laid out as follows (X=Empty, Astronomical Layout shown - X axis can be swapped for geographic maps):
QGET_STRING To get a string from the keyboard without echoing it to the screen.
QSIMP Integrate using Simpson's rule to specified accuracy. Integrate a function to specified accuracy using the extended trapezoidal rule. Adapted from algorithm in Numerical Recipes, by Press et al. (1992, 2nd edition), Section 4.2. This procedure has been partly obsolete since IDL V3.5 with the introduction of the intrinsic function QSIMP(), but see notes below.
QTRAP Integrate using trapezoidal rule to specified accuracy. Integrate a function to specified accuracy using the extended trapezoidal rule. Adapted from Numerical Recipes (1992, 2nd edition),
QUADTERP Quadratic interpolation of X,Y vectors onto a new X grid Quadratically interpolate (3 point Lagrangian) a function Y = f(X) at specified grid points. Use LINTERP for linear interpolation
RADEC To convert RA and Dec from decimal to sexigesimal units. The conversion is to sexigesimal hours for RA, and sexigesimal degrees for declination.
RANDOMP Generates an array of random numbers distributed as a power law.
RDFITS_STRUCT Read an entire FITS file (all extensions) into a single IDL structure. Each header, image or table array is placed in a separate structure
RDFLOAT Quickly read a numeric ASCII data file into IDL floating pt. vectors. Columns of data may be separated by commas or spaces. This program is fast but is restricted to data files where all columns can be read as floating point (or all double precision). Use READCOL if greater flexibility is desired. Use READFMT to read a fixed-format
RDPLOT Like CURSOR but with a full-screen cursor and continuous readout option This program is designed to essentially mimic the IDL CURSOR command, but with the additional options of continuously printing out the data values of the cursor's position, and using a full-screen cursor rather than a small cross cursor. The Full screen cursor uses OPLOT and X-windows graphics masking to emulate the cursor. One difference is that IF the PRINT keyword is set but the DOWN, WAIT, or CHANGE keywords are not set, then the leftmost mouse button will print a "newline" line-feed, but not exit.
RDPSF Read the FITS file created by GETPSF in the DAOPHOT sequence Combines the Gaussian with the residuals to create an output PSF array.
READCOL Read a free-format ASCII file with columns of data into IDL vectors Lines of data not meeting the specified format (e.g. comments) are ignored. Columns may be separated by commas or spaces.
READFITS Read a FITS file into IDL data and header variables. Under Unix, READFITS() can also read gzip or Unix compressed FITS files. See http://idlastro.gsfc.nasa.gov/fitsio.html for other ways of reading FITS files with IDL.
READFMT Quickly read a fixed format ASCII data file into IDL variables. Lines of data not meeting the specified format (e.g. comments) are ignored. To read a free format ASCII data file use the procedures READCOL or RDFLOAT.
READ_KEY To read a keystroke and return its ASCII equivalent If an ESCAPE sequence was produced and the sequence is recognized (e.g. up arrow), then a code is returned.
RECPOL Convert 2-d rectangular coordinates to polar coordinates.
REDSHIFT Interactively converts between redshift, Recession velocity, & Distance This simple program assumes a linear Hubble law and no cosmological constant. For more general and precise conversions use the program
REMCHAR Remove all appearances of character (char) from string (st)
REMOVE Contract a vector or up to 7 vectors by removing specified elements
REM_DUP Function to remove duplicate values from a vector.
REPCHR Replace all occurrences of one character with another in a text string.
REPSTR Replace all occurences of one substring by another. Meant to emulate the string substitution capabilities of text editors
REWIND Emulates the VMS REWIND function in Unix. Emulates the VMS REWIND function in the Unix environment.
RINTER Cubic interpolation of an image at a set of reference points. This interpolation program is equivalent to using the intrinsic INTERPOLATE() function in IDL V5.0 or later with CUBIC = -0.5. However, RINTER() has two advantages: (1) one can optionally obtain the X and Y derivatives at the reference points, and (2) if repeated interpolation is to be applied to an array, then some values can be pre-computed and stored in Common. RINTER() was originally for use with the DAOPHOT procedures, but can also be used for general cubic interpolation.
SCREEN_SELECT Allow a user to make an interactive screen selection from a list This procedure determines whether to use the dumb terminal version, or the widget version by examining the !D.NAME system variable.
SCR_ATTRIB To set the screen attribute to those given, in the given order.
SCR_CHARSET To change the character sets.
SCR_CURMOV To mov the cursor around the screen relative to its original position.
SCR_CURPOS To position the cursor at the specified screen location. Unspecified coordinates are set to one. Please note that the ESCAPE sequence expects the coordinates to be counted from (1,1).
SCR_ERASE To erase portions of the terminal screen.
SCR_OTHER To allow the user to issue any ESCAPE sequence.
SCR_RESET To reset the terminal.
SCR_SCROLL Define the scrolling area on the screen. Please note that the line coordinates should be counted from 1.
SELECT_O Dumb-terminal routine to let a user interactively select from a list This is the non-widget version of SCREEN_SELECT
SELECT_W Create a non-exclusive widget menu of items More than one item may be selected or 'de-selected'. Normally called by SCREEN_SELECT
SIGMA_FILTER Replace pixels more than a specified pixels deviant from its neighbors Computes the mean and standard deviation of pixels in a box centered at each pixel of the image, but excluding the center pixel. If the center pixel value exceeds some # of standard deviations from the mean, it is replaced by the mean in box. Note option to process pixels on the edges.
SIGRANGE() Selects the most significant data range in an image. Selects out the most significant range in the data to be used in displaying images. The histogram of ARRAY is used to select the most significant range. Useful for scaling an image display.
SIXLIN Compute linear regression coefficients by six different methods. Adapted from the FORTRAN program (Rev. 1.1) supplied by Isobe, Feigelson, Akritas, and Babu Ap. J. Vol. 364, p. 104 (1990). Suggested when there is no understanding about the nature of the scatter about a linear relation, and NOT when the errors in the variable are calculable.
SIXTY() Converts a decimal number to sexigesimal. Reverse of the TEN() function.
SIZE_STRUCT Obtain the size in bytes of an IDL structure definition. For most applications this function is superceded by use of the /LENGTH keyword to the intrinsic N_TAGS function introduced in IDL V2.3.0
SKIPF Emulates the VMS SKIPF function on UNIX machines. Emulates the VMS SKIPF function on UNIX machines.
SKY Determine the sky level in an image using the the procedure MMM Approximately 4000 uniformly spaced pixels are selected for the computation. Adapted from the DAOPHOT routine of the same name.
SKYADJ_CUBE Sky adjust the planes of a datacube. When removing cosmic rays from a set of images, it is desirable that all images have the same sky level. This procedure (called by CR_REJECT) removes the sky from each image in a data cube.
SPEC_DIR Complete a file specification by appending the default disk or directory
SPHDIST Angular distance between points on a sphere.
SPLINE_SMOOTH Compute a cubic smoothing spline to (weighted) data Construct cubic smoothing spline (or give regression solution) to given data with minimum "roughness" (measured by the energy in the second derivatives) while restricting the weighted mean square distance of the approximation from the data. The results may be written to the screen or a file or both and are optionally returned in the parameters. The results may be optionally displayed graphically.
SRCOR Correlate the source positions found on two lists.
STARAST Compute astrometric solution using positions of 2 or 3 reference stars Computes an exact astrometric solution using the positions and coordinates from 2 or 3 reference stars. If 2 stars are used, then the X and Y plate scales are assumed to be identical, and the axis are assumed to be orthogonal. Use of three stars will allow a unique determination of each element of the CD matrix.
STORE_ARRAY Insert array INSERT into the array DESTINATION The dimensions of the DESTINATION array are adjusted to accomodate the inserted array.
STRD Open an STSDAS file and read into an image array and header. Combines the functions of SXREAD and SXOPEN.
STREBCASC Function to converts an EBCDIC string to its ASCII equivalent Similar to the IDL Version 1 routine of the same name.
STRN Convert a number to a string and remove padded blanks. The main and original purpose of this procedure is to convert a number to an unpadded string (i.e. with no blanks around it.) However, it has been expanded to be a multi-purpose formatting tool. You may specify a length for the output string; the returned string is either set to that length or padded to be that length. You may specify characters to be used in padding and which side to be padded. Finally, you may also specify a format for the number. NOTE that the input "number" need not be a number; it may be a string, or anything. It is converted to string.
STRNUMBER Function to determine if a string is a valid numeric value.
STR_INDEX() Get indices of a substring (SUBSTR) in string. The IDL intrinsic function STRPOS returns only the index of the first occurrence of a substring. This routine calls itself recursively to get indices of the remaining occurrences.
STSUB Subroutine of STSUBIM to read a subset of a SDAS image file. User can specify a subimage range or a step size Called by STSUBIM
STSUBIM Open an STSDAS file and read a portion of the file into an array. An enhanced version of STRD. Program will prompt for the file name and subimage bounds.
STWRT Write a STSDAS header and/or 2-D array to disk (without groups!)
ST_DISKREAD Read HST FITS formatted disk files and reconstruct GEIS (STSDAS) files.
ST_DISK_DATA Routine to read next header and data array from an HST FITS disk file. This is a subroutine of ST_DISKREAD and not intended for stand alone
ST_DISK_GEIS Routine to construct GEIS files from ST FITS disk files.
ST_DISK_TABLE Routine to read FITS table from an ST fits on disk. This is a subroutine of st_diskread and not intended for stand alone
SUBSTAR Subtract a scaled point spread function at specified star position(s). Part of the IDL-DAOPHOT photometry sequence
SUNPOS To compute the RA and Dec of the Sun at a given date.
SUNSYMBOL Return the Sun symbol as a subscripted postscript character string Returns the Sun symbol (circle with a dot in the middle) as a (subscripted) postscript character string. Needed because although the Sun symbol is available using the vector fonts as the string '!9n', it is not in the standard postscript set.
SXADDHIST Procedure to add history line(s) to a FITS header
SXADDPAR Add or modify a parameter in a FITS header array.
SXDELPAR Procedure to delete a keyword parameter(s) from a FITS header
SXGINFO Return information on all group parameters in an STSDAS header. Return datatype, starting byte, and number bytes for all group parameters in an STSDAS file. Obtaining these values greatly speed up execution time in subsequent calls to SXGPAR.
SXGPAR Obtain group parameter value in SDAS/FITS file
SXGREAD Read group parameters from a Space Telescope STSDAS image file
SXHCOPY Copies selected portions of one header to another
SXHEDIT Routine to interactively edit an STSDAS header on disk. VMS: uses EDT. Unix: uses whatever your EDITOR environment variable is set to.
SXHMAKE Create a basic STSDAS header file from an IDL data array
SXHREAD Procedure to read a STSDAS header from disk. This version of SXHREAD can read three types of disk files (1) VMS Fixed record length 80 byte files, or GEIS files with
SXHWRITE Procedure to write an STSDAS or FITS header to disk as a *.hhh file.
SXMAKE Create a basic ST header file from an IDL array prior to writing data.
SXOPEN Open a Space Telescope formatted (STSDAS) header file. Saves the parameters required subsequent SX routines in the common block Stcommn. Optionally save the header in the string array Header, and the history in the string array History. Open the data file associated with this header on the same unit.
SXPAR Obtain the value of a parameter in a FITS header
SXREAD Read a Space Telescope STSDAS image file
SXWRITE Write a group of data and parameters in ST format to a STSDAS data file.
TABINV To find the effective index of a function value in an ordered vector.
TABLE_APPEND Routine to append STSDAS tables to create a single table. Input tables must all have identical columns.
TABLE_CALC Adds a new table column from a expression using existing columns
TABLE_CONV Convert STSDAS table(s) to the host format If on a BIG_ENDIAN machine (e.g. SparcStation), assumes table came from a little endian machine unless /FROM_VMS keyword is set If on a LITTLE_ENDIAN machine (e.g. OSF, Windows), assumes table came from a big endian machine unless /FROM_VMS keyword is set If on a VMS machine, assumes table came from a big endian machine unless the /FROM_LITTLE keyword is set
TABLE_DELETE Delete specified rows from an STSDAS table
TABLE_EXT Routine to extract columns from an STSDAS table
TABLE_HELP Procedure to decribe an SDAS table file.
TABLE_LIST List the contents of an STSDAS table. Procedure to list contents of an STSDAS table. This does not print the table in tabular form but instead for each row prints the column name followed by its value (one column per
TABLE_PRINT Routine to print an stsdas table.
TABLE_SORT Procedure to sort an STSDAS table by the specified column
TAB_ADDCOL Procedure to add a new column to an existing STSDAS table.
TAB_COL Procedure to extract column information from table control block
TAB_CREATE Procedure to create a new table file.
TAB_DEL Delete specified row(s) from an STSDAS table
TAB_EXPAND routine to expand the size of an SDAS table file.
TAB_FORTOSPP Procedure to convert a FORTRAN format to an SPP format specfication.
TAB_MODCOL Modify column description in a STSDAS table
TAB_NULL function to locate null values within a vector of values from an STSDAS table.
TAB_NULLROW Insert null row(s) into a STSDAS table
TAB_PRINT Routine to print an stsdas table.
TAB_PUT Procedure to place new values into a STSDAS table.
TAB_READ Procedure to read an SDAS table file
TAB_SIZE Routine to extract the table size from a table control block
TAB_SORT Procedure to sort table by the specified column
TAB_SPPTOFOR This procedure converts an spp format specification to a normal Fortran format specification.
TAB_VAL Routine to read a column from an SDAS table file
TAB_WRITE Routine to write an stsdas table to disk
TAG_EXIST() To test whether a tag name exists in a structure. Routine obtains a list of tagnames and tests whether the requested one exists or not. The search is recursive so if any tag names in the structure are themselves structures the search drops down to that level. (However, see the keyword TOP_LEVEL).
TAPRD Emulates VMS TAPRD procedure on UNIX machines. Emulates VMS TAPRD procedure on UNIX machines. However, the actions of this routine may differ from the VMS equivalent in nonstandard situations.
TAPWRT Emulates VMS TAPWRT procedure on UNIX machines. Emulates VMS TAPWRT procedure on UNIX machines.
TBDELCOL Delete a column of data from a FITS binary table
TBDELROW Delete specified row or rows of data from a FITS binary table
TBGET Return value(s) from specified column in a FITS binary table
TBHELP Routine to print a description of a FITS binary table header
TBINFO Return informational structure from a FITS binary table header.
TBPRINT Procedure to print specified columns & rows of a FITS binary table
TBSIZE Procedure to return the size of a FITS binary table.
TEN() Converts a sexigesimal number to decimal. Inverse of the SIXTY() function.
TENV() Converts sexigesimal number or vector to decimal. Like TEN() but allows vector input.
TEXTCLOSE Close a text outpu file previously opened with TEXTOPEN procedure to close file for text output as specifed by the (non-standard) system variable !TEXTOUT.
TEXTOPEN Open a device specified by TEXTOUT with unit !TEXTUNIT Procedure to open file for text output. The type of output device (disk file or terminal screen) is specified by the TEXTOUT keyword or the (nonstandard) system variable !TEXTOUT.
TICLABELS Create tic labels for labeling astronomical images. Used to display images with right ascension or declination axes. This routine creates labels for already determined tic marks (every other tic mark by default)
TICPOS Specify distance between tic marks for astronomical coordinate overlays User inputs number an approximate distance between tic marks, and the axis length in degrees. TICPOS will return a distance between tic marks such that the separation is a round multiple in arc seconds, arc minutes, or degrees
TICS Compute a nice increment between tic marks for astronomical images. For use in labelling a displayed image with right ascension or declination axes. An approximate distance between tic marks is input, and a new value is computed such that the distance between tic marks is in simple increments of the tic label values.
TIC_ONE Determine the position of the first tic mark for astronomical images. For use in labelling images with right ascension and declination axes. This routine determines the position in pixels of the first tic.
TINIT Position a tape for appending a new file To position a tape for append a new file by placing it between the final double EOF marks. (VMS or Unix IDL only)
TO_HEX Translate a non-negative decimal integer to a hexadecimal string
TRAPZD Compute the nth stage of refinement of an extended trapezoidal rule. This procedure is called by QSIMP and QTRAP. Algorithm from Numerical Recipes, Section 4.2. TRAPZD is meant to be called iteratively from a higher level procedure.
TRIM Converts numbers to strings, without trailing zeros. Converts numbers into a string representation, and trims off leading and/or trailing blanks. Differs from STRTRIM in that trailing zeros after the period are also trimmed off, unless NUMBER is already a string, or an explicit format is passed.
TSC Interpolate an irregularly sampled field using a Triangular Shaped Cloud This function interpolates an irregularly sampled field to a regular grid using Triangular Shaped Cloud (nearest grid point gets weight 0.75-dx^2, points before and after nearest grid points get weight 0.5*(1.5-dx)^2, where dx is the distance from the sample to the grid point in units of the cell size).
TSUM Trapezoidal summation of the area under a curve.
TVBOX Draw a box(es) or rectangle(s) of specified width Positions can be specified either by the cursor position or by supplying a vector of X,Y positions.
TVCIRCLE Draw circle(s) of specified radius at specified position(s) If a position is not specified, and device has a cursor, then a circle is drawn at the current cursor position.
TVELLIPSE Draw an ellipse on the current graphics device.
TVLASER Prints screen or image array onto a Postscript file or printer. Information from FITS header is optionally used for labeling.
TVLIST Cursor controlled listing of image pixel values in a window.
T_APER Driver procedure (for APER) to compute concentric aperture photometry. Data is read from and written to disk FITS ASCII tables. Part of the IDL-DAOPHOT photometry sequence
T_FIND Driver procedure (for FIND) to locate stars in an image. Finds positive brightness perturbations (i.e stars) in a 2 dimensional image. Output is to a FITS ASCII table.
T_GETPSF Driver procedure (for GETPSF) to generate a PSF from isolate stars. Generates a point-spread function from one or more isolated stars. List of stars is read from the FITS ASCII table output of T_APER. PSF is represented as a sum of a Gaussian plus residuals. Ouput residuals are written to a FITS image file.
T_GROUP Driver procedure (for GROUP) to place stars in non-overlapping groups. This procedure is part of the DAOPHOT sequence that places star positions with non-overlapping PSFs into distinct groups Input and output are to FITS ASCII tables
T_NSTAR Driver procedure (for NSTAR) for simultaneous PSF fitting. Input and output are to disk FITS ASCII tables.
T_SUBSTAR Driver procedure (for SUBSTAR) to subtract scaled PSF values Computes residuals of the PSF fitting program
UNZOOM_XY Converts X, Y position on the image display to the the X,Y position on the corresponding image array. (These positions are identical only for an unroamed, unzoomed image with with pixel (0,0) of the image placed at position (0,0) on the TV.)
UVBYBETA Derive dereddened colors, metallicity, and Teff from Stromgren colors. Adapted from FORTRAN routine of same name published by T.T. Moon, Communications of University of London Observatory, No. 78. Can be used either interactively or called from a main procedure.
VACTOAIR Convert vacuum wavelengths to air wavelengths Corrects for the index of refraction of air under standard conditions. Wavelength values below 2000 A will not be altered. Accurate to
VALID_NUM Project : SOHO - CDS Name : VALID_NUM() Purpose : Check if a string is a valid number representation.
VECT Print a set of numbers as a string with delimiters included This function returns the given vector in parenthesized coordinates as in the form (X,Y). No limit on the number of dimensions. Also note that the vector does not need to be numbers. It may also be a string vector. e.g. ['X','Y']
VSYM Create "Mongo"-like polygonal plot symbols This procedure generates a subset of Mongo-like plot symbols. The symbols are the rotationally symmetric ones that have a specified number of vertices and are either open or filled. (The half-filled symbols are not included.) After defining the plot symbol with VSYM, make the call to PLOT (or PLOTS or OPLOT) with
WCSSPH2XY Convert spherical coordinates to x and y (map) angular coordinates Convert spherical (longitude and latitude -- sky) coordinates to x and y (map) angular coordinates. This procedure is the inverse of WCSXY2SPH. See WCS_DEMO for example of use.
WCSXY2SPH Convert x and y (map) coordinates to spherical coordinates To convert x and y (map) coordinates to spherical (longitude and latitude or sky) coordinates. This procedure is the inverse of
WCS_DEMO Demonstrate the basic capabilities of procedures WCSSPH2XY & WCSXY2SPH
WCS_ROTATE Rotate between standard (e.g. celestial) and native coordinates Computes a spherical coordinate rotation between native coordinates and standard celestial coordinate system (celestial, Galactic, or ecliptic). Applies the equations in Appendix B of the paper "Representation of Celestial Coordinates in FITS" by Mark Calabretta Eric Greisen (2000, A&AS, submitted) See http://www.cv.nrao.edu/fits/documents/wcs/wcs.html
WEOF Emulates the VMS WEOF routine on UNIX machines. Emulates the VMS WEOF routine on UNIX machines.
WFPC2_READ Read WFPC2 images in either FITS or STSDAS format into IDL variables. This a versatile procedure for reading Wide Field Planetary Camera 2 (WFPC2) images. One can read either FITS or STSDAS format, and specific chip or chips. One can also read all four chips into a "batwing" mosaic-- so-called because the PC chip (chip 1) has a plate scale of 0.045", while the other three WF chips have a plate scale of 0.1"
WFPCREAD Read designated header and chip of a WFPC1 image This procedure is designed to read the designated header and chip of a WFPC image. If the PAR input parameter is supplied, then the group PARameter byte array is is returned. If it is not, then the header is modified by placing all the group parameters in the header as data
WHERENAN Find the indices of all IEEE NaN values in an array. Find the positions of all values within an array that correspond to the IEEE NaN (not-a-number) special values.
WHERE_NEGZERO() Find positions of IEEE -0.0 values. Finds the positions of all values within an array that correspond to the IEEE value -0.0, as determined from the bit pattern. Prior to IDL V5.1, the VMS operating system had trouble coping with these values. If using any other operating system, then no action is performed.
WHERE_TAG Like WHERE but works on structure tag names Obtain subscripts of elements in structure array for which a particular Tag has values in a range or matching specified values. Like the WHERE function but for use with structures
WRITEFITS Write IDL array and header variables to a disk FITS file. A minimal FITS header is created if not supplied. WRITEFITS works for all types of FITS files except random groups
XMEDSKY Subtract sky from an image as a 1-D function of X The sky is the column-by-column median of pixels within 3 sigma of the image global median. Default is [32, 1023, 12, 499], appropriate for STIS slitless spectra binned 1 X 2. This procedure is called by the cosmic ray rejection routine
XY2AD Compute R.A. and Dec from X and Y and a FITS astrometry structure The astrometry structure must first be extracted by EXTAST from a FITS header. A tangent (gnomonic) projection is computed directly; other projections are computed using WCSXY2SPH. Angles are returned in degrees. XY2AD is meant to be used internal to other procedures. For interactive purposes use XYAD.
XYAD Use a FITS header to convert pixel (X,Y) to celestial coordinates Use astrometry in a FITS image header to compute R.A. and Dec in decimal degrees from X and Y.
XYXY To use a pair of headers to convert X/Y positions from one frame
XYZ Calculate geocentric X,Y, and Z and velocity coordinates of the Sun Calculates geocentric X,Y, and Z vectors and velocity coordinates (dx, dy and dz) of the Sun. (The positive X axis is directed towards the equinox, the y-axis, towards the point on the equator at right ascension 6h, and the z axis toward the north pole of the equator). Typical position accuracy is <1e-4 AU (15000 km).
YDN2MD Convert from year and day number of year to month and day of month.
YMD2DN Convert from year, month, day to day number of year.
ZANG Determine the angular size of an object as a function of redshift Requires an input size in kpc and returns an angular size in arc seconds Default cosmology has a Hubble constant of 70 km/s/Mpc, Omega (matter) =0.3 and a normalized cosmological constant Lambda = 0.7; however these values can be changed with apropriate keywords.
ZBRENT Find the zero of a 1-D function up to specified tolerance.
ZENPOS Return the zenith RA and Dec in radians for a given Julian date.
ZOOM_XY Converts X, Y position on the image array to the the X,Y position in the current window. (These positions are identical only for an unroamed, zoomed image with with pixel (0,0) of the image placed at position (0,0) on the TV.)
ZPARCHECK Routine to check user parameters to a procedure