Python pylab errorbar和pandas的问题

当我尝试同时使用pandas和pylab.errorbar时，会收到一条非常混乱的错误消息

我有一个名为summary的数据框：

   year  treatment        SE      mean test
0  2012    Control  0.452069  0.904387    A
1  2012  Pesticide  0.246149  1.365210    B
2  2013    Control  1.073697  3.649746    A
3  2013  Pesticide  1.234574  2.593122    B

当我尝试绘制errorbar图时：

for n in summary['treatment'].unique():
    py.errorbar(summary[summary['treatment'] == n]['year'], 
                summary[summary['treatment'] == n]['mean'], 
                summary[summary['treatment'] == n]['SE'])

我得到这个错误：

Traceback (most recent call last):
  File "/opt/local/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/site-packages/IPython/core/interactiveshell.py", line 2827, in run_code
    exec code_obj in self.user_global_ns, self.user_ns
  File "<ipython-input-171-12bf2023b562>", line 2, in <module>
    py.errorbar(summary[summary['treatment'] == n]['year'], summary[summary['treatment'] == n]['mean'], summary[summary['treatment'] == n]['SE'])
  File "/opt/local/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/site-packages/matplotlib/pyplot.py", line 2697, in errorbar
    errorevery=errorevery, capthick=capthick, **kwargs)
  File "/opt/local/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/site-packages/matplotlib/axes.py", line 5749, in errorbar
    iterable(yerr[0]) and iterable(yerr[1])):
  File "/Library/Python/2.7/site-packages/pandas/core/series.py", line 618, in __getitem__
    return self.index.get_value(self, key)
  File "/Library/Python/2.7/site-packages/pandas/core/index.py", line 724, in get_value
    return self._engine.get_value(series, key)
  File "index.pyx", line 96, in pandas.index.IndexEngine.get_value (pandas/index.c:2873)
  File "index.pyx", line 104, in pandas.index.IndexEngine.get_value (pandas/index.c:2685)
  File "index.pyx", line 148, in pandas.index.IndexEngine.get_loc (pandas/index.c:3422)
  File "hashtable.pyx", line 382, in pandas.hashtable.Int64HashTable.get_item (pandas/hashtable.c:6570)
  File "hashtable.pyx", line 388, in pandas.hashtable.Int64HashTable.get_item (pandas/hashtable.c:6511)
KeyError: 0

这是：

py.errorbar(summary[summary['treatment'] == 'Pesticide']['year'],
            summary[summary['treatment'] == 'Pesticide']['mean'],
            yerr = summary[summary['treatment'] == 'Control']['SE'], fmt = 'o')

但不是这个：

py.errorbar(summary[summary['treatment'] == 'Pesticide']['year'],
            summary[summary['treatment'] == 'Pesticide']['mean'],
            yerr = summary[summary['treatment'] == 'Pesticide']['SE'], fmt = 'o')

因此，在耶尔的“杀虫剂”处理是造成问题的原因。我在过去成功地使用了类似的循环，因此有一些特定于此设置。注意：我还使用了“test”列代替了“treatment”列，得到了相同的错误

---

思考一下为什么会失败？

错误看起来与mpl无关。

summary[summary['treatment']=='mediator']['SE']

工作正常吗？\n我还发现，如果我将yerr转换为numpy数组，如np.array（summary…['SE']），它工作正常。我只是不明白为什么我需要在这里这样做，而我以前没有。您是否升级到最新的

pandas

？他们改变了

系列

而不是最近从Ndarray派生出来的，Ndarray破坏了mpl中的各种东西。我不这么认为。我用的是熊猫0.12.0。这段代码可以很好地处理另一组数据。这一套有点特别。

py.errorbar(summary[summary['treatment'] == 'Pesticide']['year'],
            summary[summary['treatment'] == 'Pesticide']['mean'],
            yerr = summary[summary['treatment'] == 'Pesticide']['SE'], fmt = 'o')