How many plotting engines do we have?

[Jordi Gutierrez Hermoso]

It could be useful to have a list somewhere of plotting engines that
are available for Octave. Is such a list compiled anywhere? I can
think off the top of my head of

    - octaviz
    - gnuplot
    - plplot
    - octplot
    - glplot

all with varying degrees of functionality and completion. Except for
gnuplot and plplot, they're all in the alpha stage of development, it
seems. I'm almost sure that there are more engines out there that I
don't know or I have forgotten about.

Maybe I should be lurking in the octave-graphics list. :-)

Curious,
- Jordi G. H.