axis manipulations in plots are unnecessarily restrictive

[John W. Eaton]

On  6-Mar-2008, Rob Mahurin wrote:

| The change to "graphics handle" plot manipulation has made some  
| tweaks to gnuplot's default axes impossible.  I have (somewhat)  
| rewritten them in the new language and would be glad to see them  
| officially supported in a later version of Octave.

| 	# eliminate the tics, but keep the box
| 	set(gca,"visible","lines");

Try

  set (gca, "xtick", [], "ytick", []);

instead.

| A statement like
| 	set(gca,"thickness",0);
| should send "set border lw 0;\n" to the gnuplot backend.

I think the correct property name for this is "linewidth", and it has
already been added to the current development sources, though nothing
is done with the new property in the __go_draw_axes__ function yet, so
I just made the attached change.

| It should be possible to use produce formatted ticklabels, e.g.	
| 	set(gca,"xticklabels","%.3f");

I don't think Matlab's ticklabels properties have this feature, though
it might be a useful to have it.

| Until Octave implements this, the backend's formatting options should  
| be available.

The goal is not to expose every feature of a particular graphics
backend, but to provide Matlab compatible graphics functionality.  We
think that's what most users of Octave want and expect, so that's what
we are aiming for.  Eventually, I doubt that gnuplot will be the
default backend because.  If you want all the features of gnuplot, I
suggest you write your data to a file and use gnuplot directly.

| I don't know where to add handle members like "thickness" or  
| "formatlabels" to make those two changes optional: set() correctly  
| refuses to add new members.

Plot properties are handled in src/graphics.h.in and src/graphics.cc.

jwe