MEAN_BY_RADAZ
Name
MEAN_BY_RADAZ
Purpose
Calculates the mean value of an image in bins of both radius and
pie slices of azimuthal angle.
Category
Astro
Calling Sequence
Result = MEAN_BY_RADAZ(Image)
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
radial bin (tagged 'RADIAL_AXIS'), the image mean within each radial
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