unfold_weights

This IDL function returns the full sky map of the weights to be applied to a HEALPix map in order to improve the quadrature. The input weights can be either ring-based or pixel-based, and read from file with user provided path, or from files with standardized name and location (ie, !healpix.path.data+'weight_ring_n?????.fits' and !healpix.path.data+'weight_pixel_n?????.fits'

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

FORMAT

IDL>weight_map = unfold_weights (Nside, [Dim, /PIXEL, /RING, SCHEME=, DIRECTORY=, /HELP, /SILENT])

IDL>weight_map = unfold_weights (File, [Dim, /HELP, /SILENT])

QUALIFIERS

Nside

HEALPix resolution parameter (scalar integer), should be a valid Nside (power of 2 in $\{1,\ldots,2^{29}\}$)

File

Input weight file to be read. If not provided, the function will try to guess the relevant file path based on Nside, the optional DIRECTORY, and the weighting scheme which must be set, with either RING, PIXEL or SCHEME

Dim

dimension of output, either 1 or 2. default:1

weight_map

output: vector of size N_pix=12N_side² if Dim=1, array of size (N_pix,3) if Dim=2 (in the latter case, all three columns are identical).

KEYWORDS

DIRECTORY=

directory in which to look for the weight file default:!healpix.path.data

/HELP

if set on input, the documentation header is printed out and the function exits

/PIXEL

if set, the code will look for the pixel-based weight file corresponding the the Nside provided, in the default or provided Directory

/RING

if set, the code will look for the ring-based weight file corresponding the the Nside provided, in the default or provided Directory

SCHEME=

can be either 'PIXEL' or 'RING', setting the type of weight file the code will look for.

/SILENT

if set on input, the function works silently

DESCRIPTION

unfold_weights reads a list of weights, stored in a compact form in a FITS file, and centered on 0, either ring-based (uniform weights on each iso-latitude rings, defined on 2N_side rings), or pixel-based (defined on $N_w \simeq 0.75 N_{\mathrm{side}}^2 \simeq N_{\mathrm{pix}}/16$) and turns them into a full sky HEALPix map of quadrature weights, with RING indexing and with values centered on 1.

RELATED ROUTINES

This section lists the routines related to unfold_weights

idl

version 6.4 or more is necessary to run unfold_weights .

nside2npweights

returns the number of non-redundant pixel-based weights used for disc storage

EXAMPLE:

mollview, /hist,

unfold_weights(256, /ring), title='Ring-based weights @ Nside=256'

mollview, /hist,

unfold_weights(256, /pixel), title='Pixel-based weights @ Nside=256'

will plot the full sky map of the ring-based and pixel-based quadrature weights for N_side=256.