[matplotlib-devel] Strange bug in logarithmic plotting

Hi there,

I hit a strange but in the code for logarithmic plotting. Executing the 
following code:

----------------------------------
from matplotlib.matlab import *
plot([1.,2.],[0.01,0.2])
gca().set_yscale('log')
show()
----------------------------------

gives the following traceback:

------------------------------------
Traceback (most recent call last):
  File "./matplotlib-bug.py", line 4, in ?
    show()
  File 
"/home/nobbi/NNlab/install/lib/python2.3/site-packages/matplotlib/backends/backend_tkagg.py", 
line 68, in show
    manager.show()
  File 
"/home/nobbi/NNlab/install/lib/python2.3/site-packages/matplotlib/backends/backend_tkagg.py", 
line 284, in show
    self.canvas.draw()
  File 
"/home/nobbi/NNlab/install/lib/python2.3/site-packages/matplotlib/backends/backend_tkagg.py", 
line 135, in draw
    FigureCanvasAgg.draw(self)
  File 
"/home/nobbi/NNlab/install/lib/python2.3/site-packages/matplotlib/backends/backend_agg.py", 
line 310, in draw
    self.figure.draw(self.renderer)
  File 
"/home/nobbi/NNlab/install/lib/python2.3/site-packages/matplotlib/figure.py", 
line 254, in draw
    for a in self.axes: a.draw(renderer)
  File 
"/home/nobbi/NNlab/install/lib/python2.3/site-packages/matplotlib/axes.py", 
line 935, in draw
    self.transData.freeze()  # eval the lazy objects
ValueError: Cannot take log of nonpositive value
-------------------------------------

The appearance of this bug actually depends opn the ratio between the y-values 
given: if the factor exceeds 10, the code breaks:

[0.1,0.2] works
[0.01,0.02] works
[0.1,1.0] works
[0.1,2.0] breaks
[1.0,11.0] breaks

Also: the problem does not appear when using semilogy

I'm using cvs versions of matplotlib and Numeric on python 2.3.4

Greetings,
Norbert

-- 
_________________________________________Norbert Nemec
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