Purpose

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  This procedure is a wrapper to skymap_smooth, which creates a
  smoothed map of some function sampled at discrete points on the
  sky. This function implements sigma clipping during
  the smoothing.

Inputs

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  map: A map structure, created by map_init.pro
  x: x location (sky coordinate in degrees) of the data
  y: y location (sky coordinates in degrees) of the data
  val: Value of the quantity sampled at (x,y)
  dval: 1-sigma error on val

Keyword Parameters

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  fwhm: The fwhm of the smoothing kernel, in degrees. Defaults to
        1/100th of the map size
  truncate: The radius at which to truncate the smoothing kernel, in
            degrees. Defaults to 2 fwhm.
  emap: Set to a variable to hold the smoothed variance map
  clip: Set to a sigma clipping threshhold (see below). Defaults to
        5.
  included: Set to a variable to hold a 1/0 array, indicating which
            (x,y) pairs were used in the sigma-clipped map.
  status: Set to a variable to return the status code of the
          procedure. A value of 0 indicates success. Status = 1
          indicates that too many objects were excluded during sigma
          clipping. Status = 2 indicates that the sigma clipping
          procedure did not converge after several iterations.
  verbose: Set to a nonzero value to print messages

Output

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  On output, the map structure is populated with the sigma-clipped
  map.

Procedure

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  This program repeatedly calls skymap_smooth. After each call, data
  points which deviate from the smooth map value at (x,y) by more
  than CLIP sigma are labeled as outliers. The procedure repeats,
  ignoring outliers, until it converges on a set of outliers.

Modification History

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  March 2010: Written by Chris Beaumont