Faster graph plotting

[Bruce Sherwood]

Graph plotting with gcurve has been greatly speeded up in the case of plotting a very large number of points that are close together. Now a gcurve point that is within 2 pixels of the most recently plotted point is not sent to the Flot graph plotting package.

Also, there is a new plotting option, as now described in the Help as follows:

It is often the case that skipping points may hardly affect the display but will make graph plotting much faster, in which case it's useful to specify an interval between plotting of points (interval = -1 is the default):

interval If interval=10, a point is added to the plot only every 10th time you ask to add a point. If interval is 0, no plot is shown. If interval is -1, no points are skipped.