Re: [Pyx-user] i'd like to plot xy graphs with contour lines and labels...

[Andre W. <and...@ph...>]

Hi Loic,

On 23.04.03, Loic Chevallier wrote:
> First of all BRAVO and thanks for this great PyX module: this is exactly
> what i need for my publishing work as a scientist (astrophysics),
> disappointed by libraries like gnuplot, pgplot, plplot, and even dislin
> which are too much limited in fine-tuning graphs.

Thanks for the credit. I should mention that we (Jörg and I) are
physicits as well. We were disappointed about the all those other
solutions for creating graphs for a long time until we finally started
this PyX project already quite some time ago. While we have evaluated
quite some available software before this decision, we hopefully do a
good job in combining good features into a new, handy, but at the same
time extremely powerfull package. All this is still very much work in
progess.

> Your graph.graphxy() class is sufficient for my needs, but i frequently
> uses some contour graphs with labels, and i would really appreciate this
> functionality to be included in the next versions of PyX.

Basically there are two possibilities to reach that gool. You could
try to build just a plot style for the existing two dimensional
graphxy. (I'm aware of the fact, that building such a style is very
difficult for an outsider right now, because the graph system is not
yet polished and well documented. I hopefully will do a better job in
the future.) But I myself think, that contour plots should be
implemented more in the way it is done in gnuplot. Although a contour
plot is planar, the data it represents are 3 dimensional data. I
already started some work on a 3-dimensional graph some time ago (the
plot at the web page is one of its results), but I had to postpone
this work until other parts of the graph module become more stable
(axis, painters, etc.). The difficulty is, that changes in the
structure have to be propagated thru all the available graph types.
Thats why I postponed the creation of other graph styles right now.

I expect, that once we are at this point, where we do have a 3
dimensional graph as well (graphxyz?), we should immediately have
contour and surface plots available. But I do not expect this to
happen in the next few months. The reason is, that Jörg and I have
quite some stress in writing our PhD theses right now (finishing our
theses are scheduled for this summer). Up to that point the PyX
development is considerably reduced, but we will continue with the
project after that for sure.

There is another point I want to mention in terms of writing labels at
contour plots. Thats not an easy task. I thought about having this
possibility of attaching labels and other stuff to paths available
independend of the special purpose of contour plots. While there is
another guy (Michael Schindler) starting to attent to the PyX
development and already working in the direction of those
"decorators", I feel encouraged in forcing him to try to do those
decorators in a quite generic way. Adding labels to contour plots will
then become as easy as adding an arrow to a path!

> Of course, starting from your .py files i could try to program this by
> myself (and i will certainly try), but i'm a beginner with python and
> object-oriented programmation, so my progress will be really slow. 

If you really need that feature right now, you may just program that
independend of the exisiting graph stuff. You may use axes (see the
axis test under test/functional/test_axis.py) and do everything else
by yourself for example. I guess, thats the easiest solution, where
you can rely on PyX parts which are already stable and documented.

On the other hand it might be a good starting point to resume the 3d
graph development (what I will certainly do at some later point; may
be around this fall; there are other people asking me about 3d plots
as well). Of course, if you have the time and you want to join the
development, you could try yourself before. I would encourage you to
stay in close contact with me, if you really want to go into that.


André

-- 
by  _ _      _   And...@Ph...
   / \ \    / )  http://www.physik.uni-augsburg.de/~wobsta/
  / _ \ \/\/ /   PyX - High quality PostScript figures with Python & TeX
 (_/ \_)_/\_/          visit http://pyx.sourceforge.net/