Re: [Matplotlib-users] Problem with errorbar and log axis

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

I have the error from a table which is in log units, and the error is 
given to be symmetric in log space.

Cheers,
Markus

On 2015-04-07 16:40, Yuxiang Wang wrote:
> Typo - "standard deviation OR standard error of mean", not "OF".
>
> Sorry.
>
> Shawn
>
>
> On Tue, Apr 7, 2015 at 10:39 AM, Yuxiang Wang <yw...@vi...> wrote:
>> If you error bars denote standard deviation of standard error of mean,
>> shouldn't they be non-symmetric in log scale?
>>
>> Shawn
>>
>> On Tue, Apr 7, 2015 at 10:11 AM, Markus Haider <mar...@ui...> wrote:
>>> Hi,
>>>
>>> I am trying to make an errorbar plot with a logarithmic x-axis. I have
>>> symmetric errors in logspace, however if I plot them, the errors are not
>>> symmetric anymore, as you can see in the enclosed image. Am I
>>> misunderstanding something or is this a bug?
>>>
>>> Thanks for your help,
>>> Markus
>>>
>>> Here the code I used to produce the plot:
>>>
>>> import matplotlib.pyplot as plt
>>>
>>> import numpy as np
>>>
>>> data_x_log = np.array([13.0,15.0])
>>>
>>> data_y = np.array([0.5,1])
>>>
>>> error_x_log = np.array([0.5,1.])
>>>
>>> error_x_lower = 10**(data_x_log-error_x_log)
>>>
>>> error_x_upper = 10**(data_x_log+error_x_log)
>>>
>>> fig = plt.figure()
>>>
>>> ax = fig.add_subplot(111)
>>>
>>> ax.errorbar(10**data_x_log,data_y,xerr=[error_x_lower,error_x_upper],ls='',marker='o')
>>>
>>> ax.set_xscale('log')
>>>
>>> ax.set_xlim([1E11,1E17])
>>>
>>> ax.set_ylim([0,2])
>>>
>>> plt.savefig('error.png')
>>>
>>>
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>>
>>
>> --
>> Yuxiang "Shawn" Wang
>> Gerling Research Lab
>> University of Virginia
>> yw...@vi...
>> +1 (434) 284-0836
>> https://sites.google.com/a/virginia.edu/yw5aj/
>
>