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alm2fits
This IDL routine provides a means to write
spherical harmonic coefficients (and optional errors) and their index label
to a FITS file. Each signal is written to a separate binary table
extension. The routine also writes header information if required.
The facility is primarily designed to allow the user to write
a FITS files containing constraints for a constrained realisation
performed by the HEALPix facility synfast.
Location in HEALPix directory tree: src/idl/fits/alm2fits.pro
FORMAT IDL>
ALM2FITS, index, alm_array, fitsfile, [HDR = , /HELP, XHDR = ]
QUALIFIERS
-
index
- Long array containing the index for the corresponding
array of alm coefficients (and erralm if required). The
index i is related to l,m by the relation
i = l2 + l + m + 1
-
alm_array
- Real array of alm coefficients written to the
file. This has dimension (nl,nalm,nsig) - corresponding to
nl = number of l,m indices
nalm = 2 for real and imaginary parts of alm coefficients or
4 for above plus corresponding error values
nsig = number of signals to be written (1 for any of T E B
or 3 if ALL to be written). Each signal is stored
in a separate extension.
-
fitsfile
- String containing the name of the file to be
written.
KEYWORDS
-
HDR =
- String array containing the primary header to be written in the FITS
file.
-
/HELP
- If set, the routine documentation header is shown and the routine exits
-
XHDR =
- String array containing the extension header. If
ALL signals are required, then each extension table
is given this header.
-
- NOTE: optional header strings should NOT include the
header keywords explicitly written by this routine.
DESCRIPTION
alm2fits writes the input alm coefficients (and associated errors if
required) into a FITS file. Each signal type is written as a separate
binary table extension. Optional headers conforming
to the FITS convention can also be written to the output file. All
required FITS header keywords are automatically generated by the
routine and should NOT be duplicated in the optional header inputs.
The keywords EXTNAME and TTYPE* are now also automatically generated.
RELATED ROUTINESThis section lists the routines related to alm2fits
-
idl
- version 6.1 or more is necessary to run alm2fits.
-
fits2alm
- provides the complimentary routine to read in
alm coefficients from a FITS file.
-
lm2index
- converts the alm order and degree
(l, m) into the index i = l2 + l + m + 1 required by
alm2fits.
-
cl2fits
- routine to write a power spectrum into
a FITS file.
-
fits2cl
- routine to read/compute C(l) power spectra from a file containing C(l) or alm coefficients
-
alteralm
- utilises the output file generated by alm2fits.
-
synfast
- utilises the output file generated by alm2fits.
EXAMPLE:
alm2fits writes the coefficients stored in the variable alm
to the output FITS file alm.fits with optional headers
passed by the string variables hdr and xhdr.
Eric Hivon
2010-06-18
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