in_ring

Routine to find the pixel index of all pixels on a slice of a given ring. The output indices can be either in the RING or NESTED scheme, depending on the nest keyword.

Location in HEALPix directory tree: src/f90/mod/pix_tools.F90 

FORMAT

call in_ring( nside, iz, phi0, dphi, listir, nir, nest )

ARGUMENTS

name & dimensionality	kind	in/out	description
nside	I4B	IN	the $N_{\mathrm{side}}$ parameter of the map.
iz	I4B	IN	ring number, counted southwards from the north pole.
phi0	DP	IN	central $\phi$ position in the slice.
dphi	DP	IN	defines the size of the slice. The slice has length $2\times dphi$ along the ring with center at $phi0$.
listir(0:4*nside-1)	I4B/ I8B	OUT	The pixel indexes in the slice.
nir	I4B	OUT	the number of pixels in the slice. nir $\le 4N_{\mathrm{side}}$
nest (OPTIONAL)	I4B	IN	The pixel indexes are in the NESTED numbering scheme if nest=1, and in RING scheme otherwise.

EXAMPLE:

call in_ring(256, 10, 0, 0.1, listir, nir, nest=1)

Returns the NESTED pixel index of all pixels within 0.1 radians on each side of $\phi=0$ on the 10th ring.

MODULES & ROUTINES

This section lists the modules and routines used by in_ring.

ring2nest

conversion from RING scheme pixel index to NESTED scheme pixel index

next_in_line_nest

returns NESTED index of pixel lying to the East of the current pixel and on the same ring

RELATED ROUTINES

This section lists the routines related to in_ring

pix2ang, ang2pix

convert between angle and pixel number.

pix2vec, vec2pix

convert between a cartesian vector and pixel number.

getdisc_ring

find all pixels within a certain radius.