nside2npweights

This IDL facility provides the number pixel-based quadrature weights (in compact non-redundant form) for a given resolution parameter Nside. Because of the HEALPix layout symmetries, $N_w \simeq N_{\mathrm{pix}}/16$, allowing economical storage on disc.

Location in HEALPix directory tree: src/idl/toolkit/nside2npweights.pro 


FORMAT

IDL> Npweights=NSIDE2NPWEIGHTS (Nside [,ERROR=, /HELP])


QUALIFIERS

Nside
HEALPix resolution parameter (integer, scalar or not), should be a valid Nside (power of 2 in $\{1,\ldots,2^{29}\}$)
Npweights
number of non-redundant weights


KEYWORDS

ERROR=
error flag, set to 1 on output if Nside is NOT valid, or stays to 0 otherwise.
/HELP
if set on input, the documentation header is printed out and the routine exits


DESCRIPTION

nside2npweights outputs the number of different pixel-based weights

\begin{displaymath}N_w=\frac{(N_{\mathrm{side}}+1)(3N_{\mathrm{side}}+1)}{4}.\end{displaymath}

If the argument Nside is not valid, a warning is issued and the error flag is raised.


RELATED ROUTINES

This section lists the routines related to nside2npweights

idl
version 6.4 or more is necessary to run nside2npweights .
unfold_weights
generates a full sky map of pixel-based or ring-based quadrature weights


EXAMPLE:

Npweights = nside2npweights(256, ERROR=error)  
Npweights will be 49408 the number of pixel-based weights for the HEALPix resolution parameter 256 and error will be 0

Version 3.82, 2022-07-28