NAME: 
  gauss1d
 PURPOSE: 
  Compute a two dimensional gaussian within an array.
 DESCRIPTION:
 CATEGORY:
  Mathematical
 CALLING SEQUENCE:
  pro gauss1d,nx,ny,x,y,fwhm,array
 INPUTS:
  nx   - size of output array
           X values of the array are the array indicies, running from 0 to
           nx-1.  This is the behavior if nx is a scalar.
           In the case of nx as a vector, it is taken to be an array of the
           x values to be used.
  x    - location of gaussian in array
  fwhm - Full width at half-maximum of gaussian.
 OPTIONAL INPUT PARAMETERS:
 KEYWORD INPUT PARAMETERS:
  SIGMA - Flag, if set means that the input fwhm is the 1/e half-width.
 OUTPUTS:
  vector - Result vector with gaussian.
 KEYWORD OUTPUT PARAMETERS:
 COMMON BLOCKS:
 SIDE EFFECTS:
 RESTRICTIONS:
 PROCEDURE:
 MODIFICATION HISTORY:
  2016/12/27, Written by Marc W. Buie, Southwest Research Institute