matplotlib-devel Mailing List for matplotlib

Hi Tom,

Yes, I would find the version you suggested clearer. I mean now that I 
know how to read it the old version seems quite logical, but if it would 
have been written the way you suggested I would not have made my 
misinterpretation.

Thank you for your help,
Cheers,
Markus

Am 2013-02-09 14:04, schrieb Thomas Caswell:
> My default interpretation of errors is always relative to the value
> because that is how they are reported (100+10-20 not 100+110-80).
>
> (got your 2nd email while writing this)
>
> Would you find this clearer?  Maybe xerr and yerr should be split up
>
> xerr/yerr: [ scalar | N, Nx1, or 2xN array-like ]
> If a scalar number, len(N) array-like object, or an Nx1 array-like
> object, errorbars are drawn x/y +/- value.
> If a sequence of shape 2xN, errorbars are drawn at x/y - row1 and x/y + row2
>
> Tom
>
> On Sat, Feb 9, 2013 at 12:49 PM, Markus Haider <mar...@ui...> wrote:
>> Hi Tom,
>>
>> Thank you very much for your answer. Indeed this solves my problem. However,
>> I was wondering if the documentation on this is correct.
>> At
>> http://matplotlib.org/api/axes_api.html?highlight=errorbar#matplotlib.axes.Axes.errorbar
>> it says:
>>
>> xerr/yerr: [ scalar | N, Nx1, or 2xN array-like ]
>> If a scalar number, len(N) array-like object, or an Nx1 array-like object,
>> errorbars are drawn +/- value.
>> If a sequence of shape 2xN, errorbars are drawn at -row1 and +row2
>>
>> This sounds to me that for a 2xN argument it should be drawn from the actual
>> supplied value, or would you interpret this differently?
>>
>> Thanks,
>> Markus
>>
>> Am 2013-02-08 22:02, schrieb Thomas Caswell:
>>
>>> The bar is drawn from `y - yerr_low` to `y + yerr_upp`
>>>
>>> ax.errorbar(x + .5,y,yerr=[[y - yerr_low],[yerr_upp -
>>> y]],fmt='s',markersize=4)
>>>
>>> will get you what you want.
>>>
>>> Tom
>>>
>>> On Fri, Feb 8, 2013 at 8:41 PM, Markus Haider <mar...@ui...>
>>> wrote:
>>>> 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.
>>>>
>>>>
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>>>
>>>
>>> --
>>> Thomas Caswell
>>> tca...@gm...
>>>
>
>
> --
> Thomas Caswell
> tca...@gm...
>