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astrofrog opened this issue Jan 29, 2015 · 7 comments · Fixed by #4050
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Issue with plotting zeros in log space #4049

astrofrog opened this issue Jan 29, 2015 · 7 comments · Fixed by #4050
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@mdboom
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status: confirmed bug status: duplicate
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v2.1

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@astrofrog
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The following simple example shows an issues with zero values when calling loglog:

import matplotlib.pyplot as plt

nu = [1e2, 1e3, 1e4, 1e5, 1e6, 1e7]
fnu = [1, 1e-30, 1e-45, 0., 0., 0.]

fig = plt.figure()
ax = fig.add_subplot(1,1,1)
ax.loglog(nu, fnu, color='blue')
fig.savefig('mpl.png')

The output is:

mpl

Of course, zero is undefined in log space, but I don't understand why it defaults to plotting a value of 0.1 instead. Doing:

fnu = [1, 1e-30, 1e-45, np.nan, np.nan, np.nan]

Does the right thing on the other hand. So maybe the best solution is to replace 0 values by np.nan inside loglog?

I am using matplotlib 1.5.x with Python 3.4.
@mdboom
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mdboom commented Jan 29, 2015

Puzzling -- the values are masked out in the log scalar and have been for years. Something else is going wrong here. Investigating.

@mdboom mdboom added this to the v1.5.x milestone Jan 29, 2015
@mdboom mdboom self-assigned this Jan 29, 2015
@mdboom
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mdboom commented Jan 29, 2015

First bad commit is 91725d8 (only affects master). Looking into a solution now.

@tacaswell
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I thought I fixed this recently....

@tacaswell
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#4008

@astrofrog
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Great, thanks! That does indeed seem to be the same issue.

@tacaswell
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This is a duplicate of #3998

@mdboom mdboom mentioned this issue Jan 29, 2015
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@mdboom
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mdboom commented Jan 29, 2015

Sorry I missed that duplicate. I have a few comments about the solution over at #4008...

@mdboom mdboom mentioned this issue Jan 29, 2015
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@mdboom mdboom

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status: confirmed bug status: duplicate
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Milestone
v2.1
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Fix masked array handling mdboom/matplotlib
3 participants
@mdboom @tacaswell @astrofrog