NAME: 
  cleandat
 PURPOSE: 
  Interactive program to eliminate and smooth over bad data points.
 DESCRIPTION:

  The data are plotted to window 6, then the cursor becomes active.
  Clicking right will exit the routine.  Clicking left will select a
  point for change.  After a left click, you must click again at the
  y value to give to the corrected point.  A running display helps
  identify the current point that the cursor is nearest to in X.

  Clicking the middle button will cause the point nearest the cursor
  (in X) to be replaced by the average of its nearest neighbors.

 CATEGORY:
  2-D plotting
 CALLING SEQUENCE:
  cleandat,xval,yval
 INPUTS:
  xval - Input vector of x values.
  yval - Input vector of y values (modified).
 OPTIONAL INPUT PARAMETERS:
 KEYWORD INPUT PARAMETERS:
  TITLE - Optional title for plot
 OUTPUTS:
  yval - (potentially) cleaned version of y values.
 KEYWORD OUTPUT PARAMETERS:
 COMMON BLOCKS:
 SIDE EFFECTS:
  Uses graphics window 6 and forces its size.  !p.multi is also set to 0.
 RESTRICTIONS:
 PROCEDURE:
 MODIFICATION HISTORY:
  95/03/24, Written by Marc W. Buie, Lowell Observatory