Surface plot queries (mostly)

Community matplotlib-users
1

Hi,

I've been giving matplotlib (0.85) a spin, as a front end for
'exploring' scientific simulation results. Now I've got the data in and
had a play, there's been a few things which have confused me somewhat
about the API/features:

* Is there the equivalent of [axes].set_ydata(), but for contours or other 3d-data plots?

* pcolor seems slow, and for some reason it defaults to automatically selecting a different (overly large) automatic axis-range than contour[f] - even if it has the X&Y data. I have an irregular mesh, so I'm not sure that imshow will work properly on its own, even if I set the data range in some way.

* For some reason my install leaves me with pylab windows which have no
proper icons in the bottom button bar. I've set MATPLOTLIBDATA and
PYTHONPATH, since I installed the modules into a subdir of my home
directory.

* Closing the pylab windows using the window-manager results in the
python process continuing - should this be calling some function to
interrupt the show() function? (I'm running GTK/GTKAgg if its relevant)

Nevertheless, even with these annoyances, I'm quite happy with the results so far - it is perhaps already simpler than the system I had been using previously, and has taken very little time to get to grips with :slight_smile:
Having said that, I'm not entirely clear whether pylab is intended to be
'the' interface to matplotlib, or just a simplified front-end - it seems
quite confusing from reading some of the online documents.

Thanks for matplotlib, (I'll think of other things to ask, in time!)

···

--
Neil

2

* Is there the equivalent of [axes].set_ydata(), but for contours or other 3d-data plots?

I don't think there's a way to change the data associated with a contour plot, but plotting with imshow() returns an AxesImage object that you can set_data() on. This is no set_extent() method, so if you are also specifying an extent you will need to update it directly by setting "img._extent = (xmin, xmax, ymin, ymax)".

I have an irregular mesh, so I'm not sure that imshow will work properly on its own, even if I set the data range in some way.

There's a cookbook entry about dealing with this situation:

  http://www.scipy.org/wikis/topical_software/GriddingIrregularlySpacedData

I also recall hearing something about support for irregularly spaced data being added, but it may still be in CVS. Sourceforge just went down, so I can't check the ChangeLog and tell you for certain. :-/

Having said that, I'm not entirely clear whether pylab is intended to be
'the' interface to matplotlib, or just a simplified front-end - it seems
quite confusing from reading some of the online documents.

In my last email, I forgot to add that I rewrote a bunch of the demos to the OO API for plotting (pylab is still used to get the Figure):

  http://agni.phys.iit.edu/~kmcivor/potpourri/oo_demos.py

Ken

···

On Dec 12, 2005, at 5:56 PM, Neil Pilgrim wrote: