In BE 105 you can make a plot of your graph size vs running time with
gnuplot.  Create a file with 2 numbers per line, graph size then time.
Say its name is prim.times.  Start gnuplot with no arguments.

gnuplot

    plot "prim.times"

It should open a window with a plot in it.
If it looks like a straight line you can fiddle around to plot that line too.

    plot "prim.times", .002 + .005 * x

To save your plot to a file do this:

    set output "prim.times.ps"
    set terminal postscript color eps
    plot "prim.times", .002 + .005 * x

The plotting window disappears.
To return to plotting in a window you can see:

    set terminal x11

There is a large help interface.
To see your postscript file (outside gnuplot):

    ghostview prim.times.ps

To convert it to pdf (doing a lousy job of it probably):

    ps2pdf prim.times.ps

If you want to submit plots made with gnuplot, describe them in your README.
Don't submit screen-capture plots.  They usually look bad and the files
are very large.

--Allen