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 Nside 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 x 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 $\le 4{N_{\rm side}}$
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.

Version 3.31, 2017-01-06