在pandas中使用多个系列绘制条形图上的误差线

Question

我可以在单个系列条形图上绘制误差条,如下所示:

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,索引A的平均值与同一索引的标准偏差配对,误差条显示该值的+/-.

但是,当我尝试在同一个图中同时绘制'mean1'和'mean2'时,我不能以相同的方式使用标准偏差:

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'

我最接近我想要的输出是这样的:

df[['mean1', 'mean2']].plot(kind='bar', yerr=df[['std1', 'std2']].values.T, alpha = 0.5,error_kw=dict(ecolor='k'))

但是现在误差条没有对称绘制.相反,每个系列中的绿色和模糊条使用相同的正负误差,这就是我被卡住的地方.如何让我的多系列条形图的误差条具有与我只有一个系列时相似的外观？

更新: 似乎这已在pandas 0.14中修复,我之前正在阅读0.13的文档.我现在没有可能升级我的熊猫.稍后会做,看看结果如何.

Answer 1

罗杰,Ajean和Alios!

好吧,我终于找到了问题的答案.这是我几天来一直试图做的事情.在早期版本的Pandas中,这个问题显然是一个问题.我安装了Pandas 0.15.0,您现在可以引用另一个数据框,并将数据用于分组条形图上的误差条,就像Ceflo试图在上面做的那样.所以下面的代码现在可以在Pandas 0.15.0中使用.

import pandas as pd
import matplotlib.pyplot as plt
df = pd.DataFrame([[4,6,1,3], [5,7,5,2]], columns = ['mean1', 'mean2', 'std1', 'std2'], index=['A', 'B'])
print(df)

df[['mean1', 'mean2']].plot(kind='bar', yerr=df[['std1', 'std2']].values.T, alpha = 0.5,error_kw=dict(ecolor='k'))
plt.show()