index2lm


This IDL routine provides a means to convert the alm index i=l2 + l+ m + 1 (as returned by eg the fits2alm routine) into l and m.

Location in HEALPix directory tree: ">src/idl/misc/index2lm.pro

 


FORMAT

IDL> INDEX2LM, index, l, m


QUALIFIERS

index
Long array containing on INPUT the index
i = l2 + l + m + 1.
l
Long array containing on OUTPUT the order l. It has the same size as index.
m
Long array containing on OUTPUT the degree m. It has the same size as index.


DESCRIPTION

index2lm converts i=l2 + l+ m + 1 into (l, m). Note that the index i is only defined for $0 \le \vert m\vert\le l$.


RELATED ROUTINES

This section lists the routines related to index2lm

idl
version 6.4 or more is necessary to run index2lm.
fits2alm
reads a FITS file containing alm values.
alm2fits
writes alm values into a FITS file.
lm2index
routine complementary to index2lm: converts (l, m) into i = l2 + l + m + 1.


EXAMPLE:

index2lm, index, l, m
will return in l and m the order l and degree m such that index =l2 + l+ m + 1

Version 3.31, 2017-01-06