healpy.pixelfunc.nside2npix

healpy.pixelfunc.nside2npix(nside)

Give the number of pixels for the given nside.

Parameters:

nside : int

healpix nside parameter; an exception is raised if nside is not valid (nside must be a power of 2, less than 2**30)

Returns:

npix : int

corresponding number of pixels

Notes

Raise a ValueError exception if nside is not valid.

Examples

>>> import healpy as hp
>>> import numpy as np
>>> hp.nside2npix(8)
768

>>> np.all([hp.nside2npix(nside) == 12 * nside**2 for nside in [2**n for n in range(12)]])
True

>>> hp.nside2npix(7)
Traceback (most recent call last):
    ...
ValueError: 7 is not a valid nside parameter (must be a power of 2, less than 2**30)