CALL ERRPLT(X,YMIN,YAVG,YMAX,NPTS,DIA) -- This routine will draw
 a set of error symbols as defined by the input arrays.  FCTR: ER
 
 X,YAVG - Arrays containing the coordinates of the circle centers
          in units of the axes.
 YMIN,YMAX - Arrays containing the lower and upper limit of the 
             error bars in units of the Y-axis.
 NPTS - Number of points.
 DIA - In absolute value, the diameter of the circle in scale inches.
       If negative, a plus sign will be placed in the center of the
       circle.