Earlier versions of Octave provided plotting through the use of
gnuplot. This capability is still available. But, a newer plotting
capability is provided by access to OpenGL. Which plotting system
is used is controlled by the graphics_toolkit function. (See
Graphics Toolkits.)
The function call graphics_toolkit ("fltk") selects the
FLTK/OpenGL system, and graphics_toolkit ("gnuplot") selects the
gnuplot system. The two systems may be used selectively through the use
of the graphics_toolkit property of the graphics handle for each
figure. This is explained in Graphics Data Structures.
Caution: The FLTK toolkit uses single precision variables internally
which limits the maximum value that can be displayed to approximately
10^38. If your data contains larger values you must use the gnuplot
toolkit which supports values up to 10^308.