Repository navigation
Problem with errorbar in log scale #163
Description
Original report at SourceForge, opened Wed Sep 1 13:52:54 2010
When using log scale, if the error is larger than flux, the error bar does not plot at all:
import matplotlib as mpl
mpl.use('Agg')
import matplotlib.pyplot as plt
fig = plt.figure()
ax = fig.add_subplot(1, 1, 1)
ax.errorbar([1.],[1.],yerr=[2.])
ax.set_yscale('log')
fig.savefig('test.png')
However, I think it would make more correct to plot the line for the errorbar, and to make it go down to -infinity.
Activity
M-funk commentedon Mar 19, 2012
The error bar does plot, but for some reason, it doesn't show the vertical connecting bar. You'll see if you do this:
fig = plt.figure()
ax = fig.add_subplot(111)
ax.errorbar([1.,2.,3.],[1.,1.,1.],yerr = [0.1,3.,0.4])
ax.set_yscale('log')
fig.savefig('test.png')
something like this outputs:
http://i.imgur.com/LOIi7.png
I think the problem lies in the fact that numpy computes log(1), in any base, equal to 0
pelson commentedon Aug 19, 2012
Confirming. Pretty sure this is related to the fact that you are trying to plot an error bar down to log(0). This works if your not trying log(0). For instance:
Looks fine. @M-funk: can you confirm what you are expecting to see? I can't see that there is an action on this issue (perhaps a warning might be suitable when you are at log(0))?
neggert commentedon Mar 18, 2013
This can be worked around by doing
Maybe this should be the default for
set_yscale? This seems to cause quite a few problems.kreczko commentedon May 13, 2013
@neggert : Nice workaround.
Wish I had seen it before I wasted 1 hour to try and fix it ;)
From a beginners standpoint I would definitely vote for making it the default (unless there are obvious reasons not to do so).
mdboom commentedon May 13, 2013
👍 on making the default
clip, with the appropriate API change warning.SebastianoF commentedon Jan 24, 2019
Uhm... No, the errorbar should not be asymmetric when passing in log scale.
Please consider
http://faculty.washington.edu/stuve/uwess/log_error.pdf
If I understood correctly the documentation, I would consider nonposx="mask" as the best option of the default behavour.