XYGraph

XYGraph is one of Pablo's display functional units.  It accepts as input
either a vector or two-dimensional array of data (the array must be of
size [2,n]).  Data is plotted as points in simple X-Y form, with the option 
given to connect points with lines.


Functional Unit Inputs:  vector, array

XYGraph attributes:

	XtNheight	height (in pixels) of the widget 
	XtNwidth	width (in pixels) of the widget
	XtNbackground	color of the widget drawing area background
	XtNgridColor	color of the grid lines drawn in the plot area
	XtNnumColors	number of default colors used by XYGraph
	XtNyticks	number of tick lines drawn on the y-axis
	XtNxticks	number of tick lines drawn on the x-axis
	XtNlogx		set to TRUE if logarithmic scaling is desired along x
	XtNlogy         set to TRUE if logarithmic scaling is desired along y
	XtNautoscale	set to TRUE if autoscaling is to be used (min/max
				values ignored)
	XtNminx		minimum representable value along x
	XtNmaxx		maximum representable value along x
	XtNminy		minimum representable value along y
	XtNmaxy		maximum representable value along y
	XtNconnect	set to TRUE if points are to be connected with lines
	XtNshowTicks	set to TRUE if tick lines are to be drawn
	XtNshowRange	set to TRUE if the min/max values in x and y are to
			   be displayed 
	XtNygraphCnt	number of point sets to be maintained (each point set
			   is connected by its own line) (not implemented)
	XtNtextColor	color of the text used to display min/max information

