'Plotting error bars on grouped bars in pandas
I can plot error bars on single series barplots like so:
import pandas as pd
df = pd.DataFrame([[4,6,1,3], [5,7,5,2]], columns = ['mean1', 'mean2', 'std1', 'std2'], index=['A', 'B'])
print(df)
mean1 mean2 std1 std2
A 4 6 1 3
B 5 7 5 2
df['mean1'].plot(kind='bar', yerr=df['std1'], alpha = 0.5,error_kw=dict(ecolor='k'))

As expected, the mean of index A is paired with the standard deviation of the same index, and the error bar shows the +/- of this value.
However, when I try to plot both 'mean1' and 'mean2' in the same plot I cannot use the standard deviations in the same way:
df[['mean1', 'mean2']].plot(kind='bar', yerr=df[['std1', 'std2']], alpha = 0.5,error_kw=dict(ecolor='k'))
Traceback (most recent call last):
File "<ipython-input-587-23614d88a3c5>", line 1, in <module>
df[['mean1', 'mean2']].plot(kind='bar', yerr=df[['std1', 'std2']], alpha = 0.5,error_kw=dict(ecolor='k'))
File "C:\Users\name\Dropbox\Tools\WinPython-64bit-2.7.6.2\python-2.7.6.amd64\lib\site-packages\pandas\tools\plotting.py", line 1705, in plot_frame
plot_obj.generate()
File "C:\Users\name\Dropbox\Tools\WinPython-64bit-2.7.6.2\python-2.7.6.amd64\lib\site-packages\pandas\tools\plotting.py", line 878, in generate
self._make_plot()
File "C:\Users\name\Dropbox\Tools\WinPython-64bit-2.7.6.2\python-2.7.6.amd64\lib\site-packages\pandas\tools\plotting.py", line 1534, in _make_plot
start=start, label=label, **kwds)
File "C:\Users\name\Dropbox\Tools\WinPython-64bit-2.7.6.2\python-2.7.6.amd64\lib\site-packages\pandas\tools\plotting.py", line 1481, in f
return ax.bar(x, y, w, bottom=start,log=self.log, **kwds)
File "C:\Users\nameDropbox\Tools\WinPython-64bit-2.7.6.2\python-2.7.6.amd64\lib\site-packages\matplotlib\axes.py", line 5075, in bar
fmt=None, **error_kw)
File "C:\Users\name\Dropbox\Tools\WinPython-64bit-2.7.6.2\python-2.7.6.amd64\lib\site-packages\matplotlib\axes.py", line 5749, in errorbar
iterable(yerr[0]) and iterable(yerr[1])):
File "C:\Users\name\Dropbox\Tools\WinPython-64bit-2.7.6.2\python-2.7.6.amd64\lib\site-packages\pandas\core\frame.py", line 1635, in __getitem__
return self._getitem_column(key)
File "C:\Users\name\Dropbox\Tools\WinPython-64bit-2.7.6.2\python-2.7.6.amd64\lib\site-packages\pandas\core\frame.py", line 1642, in _getitem_column
return self._get_item_cache(key)
File "C:\Users\name\Dropbox\Tools\WinPython-64bit-2.7.6.2\python-2.7.6.amd64\lib\site-packages\pandas\core\generic.py", line 983, in _get_item_cache
values = self._data.get(item)
File "C:\Users\name\Dropbox\Tools\WinPython-64bit-2.7.6.2\python-2.7.6.amd64\lib\site-packages\pandas\core\internals.py", line 2754, in get
_, block = self._find_block(item)
File "C:\Users\name\Dropbox\Tools\WinPython-64bit-2.7.6.2\python-2.7.6.amd64\lib\site-packages\pandas\core\internals.py", line 3065, in _find_block
self._check_have(item)
File "C:\Users\name\Dropbox\Tools\WinPython-64bit-2.7.6.2\python-2.7.6.amd64\lib\site-packages\pandas\core\internals.py", line 3072, in _check_have
raise KeyError('no item named %s' % com.pprint_thing(item))
KeyError: u'no item named 0'
The closest I have gotten to my desired output is this:
df[['mean1', 'mean2']].plot(kind='bar', yerr=df[['std1', 'std2']].values.T, alpha = 0.5,error_kw=dict(ecolor='k'))

But now the error bars are not plotted symmetrically. Instead the green and blur bars in each series use the same positive and negative error and this is where I am stuck. How can I get the error bars of my multiseries barplot to have a similar appearance as when I had only one series?
Update: Seems like this is fixed in pandas 0.14, I was reading the docs for 0.13 earlier. I don't have the possibility to upgrade my pandas right now though. Will do later and see how it turns out.
Sources
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Source: Stack Overflow
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