# inRing

Return list of pixels in a ring or ring section

## Contents

- Syntax
- Input Arguments
- Return Arguments
- Description
- Example
- See also
- Requires

## Syntax

    pixList = inRing(nSide, nRing, phi0, dPhi, 'Param1', Value1, ...);

## Input Arguments

    nSide       HEALPix resolution parameter
    nRing       Ring number (1 <= nRing <= 4*nSide-1)
    phi0, dPhi  (optional) Ring section longitudes [phi-dPhi,phi+dPhi]

    Param       Value
    'nest'      return pixels with nested indexing (true | {false})
    'strict'    return only pixels whose center is in longitude range
                (true | {false})

## Return Arguments

    pixList     size(nRing) cell array of pixels in ring defined by nRing,
                phi0, dPhi

## Description

    nRing may be a numeric array, in which case phi0, dPhi and nest may each
    be either scalar or a size(nRing) array. If strict is false (default)
    then all pixels intersected by longitude range are included in pixList.

## Example

    % All pixels in ring 2 of nSide = 4 pixelization (ring indexed)
    pix = inRing(4,2);
    pix{:}

    % Same, but nested indexing
    pix = inRing(4,2,'nest',true);
    pix{:}
    nest2ring(4,pix{:})

    % Pixels in rings [2,4;8,10;12,14] and the longitude band
    % [7*pi/4,9*pi/4]
    nRing = [2,3;5,12;13,14];
    pix = inRing(4,nRing,2*pi,pi/4);
    pix{1}
    pix{end}

    % Same, with strict selection
    pix = inRing(4,nRing,2*pi,pi/4,'strict',true);
    pix{1}
    pix{end}

    ans =

         5     6     7     8     9    10    11    12

    ans =

        65    16    15    32    31    48    47    64

    ans =

       137     1     5     2     7     3     9     4

    ans =

        12     5     6

    ans =

       188   181   182

    ans =

        12     5

    ans =

       188   181

## See also

ringNum

## Requires

ring2z, pix2vec

Copyright 2010-2011 Lee Samuel Finn. Terms of Use.