我可以在单系列条形图上绘制误差线,像这样:
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'))
正如预期的那样,指标A的平均值与相同指标的标准差配对,误差线显示该值的+/-。
然而,当我尝试在同一图中绘制'mean1'和'mean2'时,我无法以同样的方式使用标准差:
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'
我最接近期望输出的结果是这个:
df[['mean1', 'mean2']].plot(kind='bar', yerr=df[['std1', 'std2']].values.T, alpha = 0.5,error_kw=dict(ecolor='k'))
现在误差条不对称地绘制出来了。 相反,每个系列中的绿色和蓝色条都使用相同的正负误差,这就是我卡住的地方。 我如何使我的多系列柱状图的误差条外观类似于只有一个系列时的外观?
更新: 看起来这在 pandas 0.14 中已经修复,我之前看的是0.13的文档。 不过我现在没有升级pandas的可能性。稍后会进行并查看结果。
error_kw
是用来做什么的? - Charlie Parker