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Semilog plots with zero values #3998

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Semilog plots with zero values#3998
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Release criticalFor bugs that make the library unusable (segfaults, incorrect plots, etc) and major regressions.status: confirmed bug
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v2.1
@raoulbq

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@raoulbq
raoulbq
opened on Jan 13, 2015

Consider the following test code:

from numpy import *
from matplotlib.pyplot import *


x = arange(-10,10)
y = (1.0 - 1.0/(x**2+1))**20

figure()
semilogy(x, y, "-o")
grid(True)
savefig("test.png")

Correct Plot (the value y=0 at x=0 is masked out from y-log plot):
test_good

Wrong Plot (spurious point at x=0 with y=1e-1):
test_wrong

A git bisect tells me that:

91725d8665975de9a26d631445ab1448b0391e1a is the first bad commit
commit 91725d8665975de9a26d631445ab1448b0391e1a
Author: Joel B. Mohler <joel@kiwistrawberry.us>
Date:   Thu Aug 21 10:43:28 2014 -0400

    use _fast_from_codes_and_verts in transform code

The commit diff introduces the use of _fast_from_codes_and_verts,
so the issue is probably somewhere deeper inside this function.

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