The 2014 "gnuplot-mode" has the problem of not rendering the greek symbols
when asked to by babel, hence, my switch to "gnuplot-mode" 2017.

C-h v gnuplot-program reports

gnuplot-program’s value is "/usr/bin/gnuplot"
  This variable may be risky if used as a file-local variable.
Documentation:
Not documented as a variable.

. . . which is correct, and, yes, as a stand-alone mode it works, i.e., it
finds the gnuplot executable and renders the greek letters fine. However,
when I attempt it inside a babel gnuplot code block it gives the error of
not finding the executable. This is behavior I've seen when babel doesn't
see a necessary mode that it requires to work with. This is my
supposition/guess. As I recall, when I first tried a babel gnuplot block,
it made this same complaint. Then I realized I hadn't installed the gnuplot
mode. The problem went away when I installed gnuplot-mode 2014. So again,
my educated guess is that babel doesn't see or want to interact with
gnuplot-mode 2017, rather, it want to see gnuplot-mode 2014.

I feel like I'm beating this to death. I can simply hand-edit in the
diagrams with greek letters done correctly into my org file, i.e., just not
do babel gnuplot. Again, gnuplot-mode 2014 in stand-alone will do a "plot
file" of the code correctly, but not a "plot buffer" strangely enough. (I'm
guessing babel gnuplot wants to do a "plot buffer".) OTOH, this is a bug,
i.e., no sane work-around, and we, an advanced species, shouldn't negotiate
with or accommodate insects.

So what is the process of keeping babel up-to-date AFA modes interacting
with their executables is concerned? Who does this? I can look at the
gnuplot-modes and see if I can find anything. But I'm a total noob with
big-time Elisp code.

On Tue, Apr 30, 2019 at 1:09 AM Fraga, Eric <e.fraga@ucl.ac.uk> wrote:

> Thanks for the long explanation.  I am using the 2014 version of
> gnuplot-mode and gnuplot 5.2.
>
> gnuplot-mode has a customizable variable, gnuplot-program, which
> specifies which command to execute to start gnuplot.  The default value
> for this variable, at least in the 2014 version, is simply "gnuplot" so
> it will pick up the default gnuplot on Linux (if there is more than one
> version installed, I imagine that /etc/alternatives will be used to
> identify the default).
>
> If you think the wrong gnuplot is being picked up, maybe customize this
> variable?  What do you get if you simply invoke "M-x run-gnuplot"?
>
> --
> Eric S Fraga via Emacs 27.0.50, Org release_9.2.3-327-g3375f0
>