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## Purpose

Calculates the mean value of an image in bins of both radius and
pie slices of azimuthal angle.

Astro

## Inputs

Image: 2D image array.

## Keyword Parameters

RBIN: Size of radial bins (in pixels). Default: 1.
NTHETA: Number of azimuthal bins. Default: 8.
CENTER: Pixel co-ordinate to consider the center. May be
non-integer, or even off the image (as long as
/CROPCIRCLE is not set). Default: Image center.
ROTATION: Start the first azimuthal bin at an angle ROTATION
(in radians) from the x-axis. Default: 0.
CROPCIRCLE: Set this keyword to crop out the corners of
the image, i.e. use only those pixels within the largest
circle that is fully enclosed in the image.
NAN: Set this keyword to check for NaN or Infinity when
calculating the means. Any such elements are treated
as missing data.

## Outputs

This function returns a structure containing the inner radii of each
bin (tagged 'RADIAL_MEAN'), the starting azimuth of each azimuthal
bin (tagged 'AZIMUTHAL_AXIS'), and the image mean within each azimuthal
pie slice (tagged 'AZIMUTHAL_MEAN'). Note that azimuthal angle is
calculated counterclockwise starting at the x-axis (unless ROTATION
is specified).

## Example

Calculate the radial and azimuthal means of some image data, cutting
out the "corners" that aren't fully sampled to the same radii. Use
radial bins 2 pixels wide and azimuthal bins 30 degrees wide.
imagedata = dist(25,25)
imagemeans = MEAN_BY_RADAZ(imagedata, RBIN=2, NTHETA=12, /CROPCIRCLE)

## Modification History

Written by: Jeremy Bailin, in response to a question by Andy Bohn.
17 June 2008 Public release in JBIU
18 June 2008 Fixed typo in documentation

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