[matplotlib-devel] Errorbar problem?

[Markus H. <mar...@ui...>]

Hi, 

I think I have a problem with errorbars in a log plot. The problem is
reproducible through the enclosed errorbar_log.py file. As you can see I
plot a point with y = 10**(-5) and I want the errorbars drawn from
10**(-5.5) to 10**(-4.5) which should be symmetric in this plot but isn't. 

Here is the content of my errorbar_log.py file: 

#!/usr/bin/python 
import numpy as np 
import matplotlib.pyplot as plt 

fig = plt.figure() 
ax = fig.add_subplot(111) 
x = 0.0 
y = 10**(-5.0) 
yerr_low = 10**(-5.5) 
yerr_upp = 10**(-4.5) 
ax.errorbar(x,y,yerr=[[yerr_low],[yerr_upp]],fmt='o',markersize=4) 
ax.set_xlim(-1.0,1.0) 
ax.set_ylim(1E-6,1E-3) 
ax.set_yscale('log') 
plt.savefig('errorbar.png') 

--------------------------------------------- 

10**(-5.5) = 3.162277660168379e-06 
and 10**(-4.5) = 3.1622776601683795e-05 

but you can see that the lower boundary is not at the calculated value. 
<http://matplotlib.1069221.n5.nabble.com/file/n40412/errorbar.png> 


Do I misunderstand the behaviour of the errorbar function or is this a bug? 

Cheers, 
Markus 



--
View this message in context: http://matplotlib.1069221.n5.nabble.com/Errorbar-problem-tp40412.html
Sent from the matplotlib - devel mailing list archive at Nabble.com.