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ring_analysis
This subroutine computes the Fast Fourier Transform of a single ring
of pixels
and extends the computed coefficients up to the maximum
m of the transform.
Location in HEALPix directory tree:
src/f90/mod/alm_tools.f90
FORMAT call ring_analysis(
nsmax, nlmax, nmmax, datain, nph, dataout, kphi0
)
ARGUMENTS
| name & dimensionality |
kind |
in/out |
description |
|---|
| |
|
|
|
|
nsmax |
I4B |
IN |
 of the map. |
| nlmax |
I4B |
IN |
Maximum l of the analysis. |
| nmmax |
I4B |
IN |
Maximum m of the analysis. |
| nph |
I4B |
IN |
The number of points on the ring. |
| datain(0:nph-1) |
DP |
IN |
Function values on the ring. |
| dataout(0:nmmax) |
DPC |
OUT |
Fourier components, replicated to Nmmax. |
| kphi0 |
I4B |
IN |
0 if the first pixel on the ring is at
 ; 1 otherwise. |
EXAMPLE:
call ring_analysis(64,128,128,datain,8,dataout,0)
Returns the periodically extended complex
Fourier Transform of datain in
dataout. They are returned in the following order: 0 1 2 3 4 5 6 7
6 5 4 3 2 1  . The value kphi0=0 specifies that no phase
factor needed to be applied, because the ring starts at .
MODULES & ROUTINESThis section lists the modules and routines used by ring_analysis.
-
healpix_fft
- module.
RELATED ROUTINESThis section lists the routines related to ring_analysis
-
ring_synthesis
- Inverse transform (complex-to-real), used in
alm2map,
alm2map_der and synfast
Eric Hivon
2010-06-18
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