pylab: figimage crashes

Hi, I have a problem. The following script crashes:

    from pylab import *

    a=arange(1500).reshape(50,30)

    figure()
    figimage(a)

    show()

Python says:

  Traceback (most recent call last):
  File "crash.py", line 5, in ?
    figimage(a)
  File "c:\Python24\lib\site-packages\matplotlib\pylab.py", line 810, in figimage
    draw_if_interactive()
  File "c:\Python24\lib\site-packages\matplotlib\backends\backend_tkagg.py", line 59, in draw_if_interactive
    figManager.show()
  File "c:\Python24\lib\site-packages\matplotlib\backends\backend_tkagg.py", line 301, in show
    self.canvas.draw()
  File "c:\Python24\lib\site-packages\matplotlib\backends\backend_tkagg.py", line 151, in draw
    FigureCanvasAgg.draw(self)
  File "c:\Python24\lib\site-packages\matplotlib\backends\backend_agg.py", line 398, in draw
    self.figure.draw(renderer)
  File "c:\Python24\lib\site-packages\matplotlib\figure.py", line 515, in draw
    im.draw(renderer)
  File "c:\Python24\lib\site-packages\matplotlib\image.py", line 473, in draw
    renderer.draw_image(self.ox, self.oy, im, self.origin, self.figure.bbox)
    IndexError: Unexpected SeqBase<T> length.

    This application has requested the Runtime to terminate it in an unusual way.
    Please contact the application's support team for more information.

As you can see, I'm using Python 2.4. Matplotlib is from the Enthought Python Edition,
version number is 0.87.2. I tried Google, but looking for "Unexpected SeqBase matplotlib" did not help me.

Any hints ?

Greetings, Uwe

Hi,

I would like to plot contours with a nonlinear mapping from values to color as follows:

   -1 -> red
    0 -> white or green or black
   +1 -> red

How can I achieve this ?

Greetings, Uwe

Uwe,

I don't know the answer to your question, but yesterday Rob Hetland sent out and email entitled "Creating a non-linear colormap." that includes example code. That might help you get started.

Ken

Uwe Schmitt wrote:

Hi,

I would like to plot contours with a nonlinear mapping from values to color as follows:

   -1 -> red
    0 -> white or green or black
   +1 -> red

How can I achieve this ?

See examples/contourf_demo.py. The relevant part is this:

# Now make a contour plot with the levels specified,
# and with the colormap generated automatically from a list
# of colors.
levels = [-2, -1.5, -1, -0.5, 0, 0.5, 1, 1.5]
CS3 = contourf(X, Y, Z, levels,
                         colors = ('r', 'g', 'b'),
                         origin=origin)

Try specifying 4 levels; I think this would do what you want (with black for the middle range, for example):

levels = [-1.5, -0.5, 0.5, 1.5]
CS = contourf(X, Y, Z, levels, colors=('r', 'k', 'r'))

Eric

···

Greetings, Uwe
   
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Ken McIvor wrote:

Uwe,

I don't know the answer to your question, but yesterday Rob Hetland sent out and email entitled "Creating a non-linear colormap." that includes example code. That might help you get started.

Ken

Thanks, but I can not access this article from the mailing lists archive.
On sourceforge the newest posting is from 23th feb.

Greetings, Uwe

I'm not sure what the problem with SourceForge is. I'll forward you that email off-list.

Ken

···

On Mar 9, 2007, at 5:11 AM, Uwe Schmitt wrote:

Thanks, but I can not access this article from the mailing lists archive.
On sourceforge the newest posting is from 23th feb.

I discovered the same problem, so I went looking and found the mailing list properly archived at nabble.com:

http://www.nabble.com/Creating-a-non-linear-colormap.-t3362841.html

Cheers,
Suresh

···

On Fri, 9 Mar 2007, Ken McIvor wrote:

On Mar 9, 2007, at 5:11 AM, Uwe Schmitt wrote:

Thanks, but I can not access this article from the mailing lists
archive.
On sourceforge the newest posting is from 23th feb.

I'm not sure what the problem with SourceForge is. I'll forward you
that email off-list.

Ken

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