Nico Schlömer wrote:
> Hi,
>
> I'm looking into replacing my MATLAB(R) plotting routines by something
> slicker, and quite naturally found matplotlib. It has all the
> capabilities that I would need, except that I can't yet transform my
> plots into TikZ.
> For MATLAB(R), I used this rather elaborate script
> <
http://win.ua.ac.be/~nschloe/content/matlab2tikz>.
>
> Well, I thought I can just go ahead and start writing and equivalent
> backend; the documentation is really nice and clear (quite unlike
> MATLAB's!) so it was no big problem to get into the concepts of the
> backend. I played around a little and thought about how I could
> implement this and that, and some questions arose which can maybe best
> answered here.
>
> For the sake of clarity, let me just give a snippet of Pgfplots (TikZ)
> code that I would like the backend to produce
>
> ===================== *snip* =====================
> [...]
> \begin{semilogyaxis}
> [axis on top,
> xtick={2,4,6,8,10,12,14,16},
> ytick={1e-15,1e-10,1e-05,1,100000},
> xmin=0.000000e+00,xmax=1.700000e+01,
> ymin=1.000000e-15,ymax=1.000000e+05,
> xmajorgrids,
> ymajorgrids,
> title={$\norm{F(\psi)}_2$},
> xlabel={$k$},
> width=\figurewidth,
> height=\figureheight,
> scale only axis
> ]
> % Line plot
> \addplot [color=red,only marks,mark=*,mark options={solid,fill=red}]
> coordinates{
> (1.000000e+00,3.206000e+01) (2.000000e+00,3.860000e+01)
> (3.000000e+00,1.421000e+03) (4.000000e+00,4.143000e+02)
> (5.000000e+00,1.445000e+02) (6.000000e+00,3.775000e+01)
> (7.000000e+00,7.455000e+00) (8.000000e+00,7.228000e-01)
> (9.000000e+00,2.275000e-02) (1.000000e+01,4.953000e-05)
> (1.100000e+01,9.718000e-10) (1.200000e+01,5.534000e-07)
> (1.300000e+01,4.217000e-11) (1.400000e+01,3.930000e-03)
> (1.500000e+01,2.067000e-07) (1.600000e+01,7.231000e-12)
> };
> \end{semilogyaxis}
> [...]
> ===================== *snap* =====================
>
> This yields a purely marker plot (without lines) on a coordinate
> system where the y-coordinate is log-scaled. You see that the code is
> rather semantic and can easily be edited (which is think is the whole
> point of Pgfplots as opposed to pure TikZ).
>
> Now, if for a matplotlib plot I had query functions for the the axes
> ranges, ticks, grids, titles, data values, and so on and so forth, it
> would be a more or less complicated parsing of those and creating what
> we see above.
>
> However, it seems to me that the concept of backends is different.
> draw_path() would be called to plot the graph itself, the coordinate
> axes, and basically everything that resembles a line, giving its
> outline (color, shape, markers, start and end points) but *no*
> semantic information, that is, whether the path is part of an axis, an
> arrow or whatever.
> Is that correct?
>
Yes -- the backend interface is designed for "dumber" output formats
that don't know anything about the semantics of plots -- PDF, PS, SVG
etc. are basically "draw a line here, put some text there" sorts of
things. Of course, you could probably write a TikZ backend without much
semantic detail fairly easily.
> Considering this, what do matplotlob masterbrains :) think would be a
> good way to extract Pgfplots code out of a matplotlib figure? Is a
> backend feasible at all? Would a function as "matplotlib2tikz(
> myFigure )" be more advisable, making use of all sorts of query
> functions? (Such as myFigure.axes.get_xlim() -- Does something like
> that exist at all?)
>
That sounds more feasible -- however, keep in mind that anything without
a public interface (a get_* method) is free to change in a future
version of matplotlib. I suspect (though haven't thought it all the way
through) that you may be required to dig into private members to get
everything you need. I also suspect that this will be a lot of work to
support all of the kinds of plots that matplotlib supports, and problems
are likely to arise when the semantics of Pgfplot and/or TikZ don't mesh
well. For example, does Pgf plot support the same set of nonlinear
transformations as matplotlib?
Other people have suggested TikZ support in the past, and I, personally,
haven't been very convinced of the usefulness of such a thing. It's
just as easy to include a PDF or EPS in LaTeX, and the mathtext and/or
usetex functionality goes a long way to making the plots blend in nicely
-- though it does take some care to control the size of the plots to
make the font sizes match, it's by no means impossible. Jae-Joon's work
with fancy arrow styles brings in a lot of the finesse features of TikZ
to matplotlib. What do you see as the use cases for a TikZ backend?
Mike
--
Michael Droettboom
Science Software Branch
Operations and Engineering Division
Space Telescope Science Institute
Operated by AURA for NASA
------------------------------------------------------------------------------
This SF.Net email is sponsored by the Verizon Developer Community
Take advantage of Verizon's best-in-class app development support
A streamlined, 14 day to market process makes app distribution fast and easy
Join now and get one step closer to millions of Verizon customers
http://p.sf.net/sfu/verizon-dev2dev
_______________________________________________
Matplotlib-devel mailing list
Matplotlib-devel@...
https://lists.sourceforge.net/lists/listinfo/matplotlib-devel
pdf-vs-tikz.pdf (60K) 
