Re: [Matplotlib-users] semilog error plots

[Gary R. <ga...@em...>]

As a followup to my reply to this (the suggestion found by searching the list archives and due to John Hunter), I tried an example errorbar plot and got a traceback. I think this is highlighting a bug as demonstrated by the following example. It's not an errorbar plot, but errorbar generates a traceback too. Danny, if you get a traceback, it'd be worth letting the list know:

from matplotlib.matlab import *
m = array([0.1, 0.2, 0.3, 0.6, 0.8, 1,  3])
r = array([18, 180, 1800, 1.8, 0.18, 250, 2.8])
semilogy(m, r)
set(gca(), "yscale", "linear")
show()

works fine


whereas


from matplotlib.matlab import *
m = array([0.1, 0.2, 0.3, 0.6, 0.8, 1,  3])
r = array([18, 180, 1800, 1.8, 0.18, 250, 2.8])
plot(m, r)
set(gca(), "yscale", "log")
show()

generates a traceback:

Traceback (most recent call last):
  File "C:\APPS\PYTHON23\Lib\site-packages\matplotlib\backends\backend_gtkagg.py", line 75, in callback
    self.draw()
  File "C:\APPS\PYTHON23\Lib\site-packages\matplotlib\backends\backend_gtkagg.py", line 42, in draw
    agg.draw()
  File "C:\APPS\PYTHON23\Lib\site-packages\matplotlib\backends\backend_agg.py", line 296, in draw
    self.figure.draw(self.renderer)
  File "C:\APPS\PYTHON23\Lib\site-packages\matplotlib\figure.py", line 130, in draw
    for a in self.axes: a.draw(renderer)
  File "C:\APPS\PYTHON23\Lib\site-packages\matplotlib\axes.py", line 597, in draw
    self.transData.freeze()  # eval the lazy objects
ValueError: Cannot take log of nonpositive value


I think both should work.
John, is this a bug?

Gary Ruben
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