NAME:
	mean
 PURPOSE: (one line)
	Compute the arithmetic mean of the data in the input array.
 DESCRIPTION:
 CATEGORY:
       Numerical
 CALLING SEQUENCE:
	val = mean(arr)
 INPUTS:
	arr - Input array.
 OPTIONAL INPUT PARAMETERS:
 KEYWORD PARAMETERS:
 OUTPUTS:
	Returns the mean of the input array.
 COMMON BLOCKS:
 SIDE EFFECTS:
 RESTRICTIONS:
 PROCEDURE:
 MODIFICATION HISTORY:
	Written by Marc W. Buie, Lowell Observatory