Question

我很难理解以下内容：

当给定列具有空值时过滤数据帧的行后，我无法创建直方图。

#!/usr/bin/python3



import pandas as pd
import numpy as np

import matplotlib.pyplot as plt


df = pd.DataFrame({'A' : [None,2,None,4],
                   'C' : pd.Series(1,index=list(range(4)),dtype='float32'),
                   'D' : np.array([3] * 4,dtype='int32'),
                   'E' : pd.Categorical(["test","train","test","train"]),
                   'F' : 'foo' })
c='A'

df=df[df['A'].notnull()]
print (df)


plt.figure()
plt.hist(df[c])
plt.show()

输出结果为：

     A    C  D      E    F
1  2.0  1.0  3  train  foo
3  4.0  1.0  3  train  foo
---------------------------------------------------------------------------
KeyError                                  Traceback (most recent call last)
/srv/logs/tiaki/sentryo/exps/tools/ttplot.py in <module>()
     32
     33 plt.figure()
---> 34 plt.hist(df[c])
     35 plt.show()
     36

/usr/lib/python3/dist-packages/matplotlib/pyplot.py in hist(x, bins, range, normed, weights, cumulative, bottom, histtype, align, orientation, rwidth, log, color, label, stacked, hold, **kwargs)
   2894                       histtype=histtype, align=align, orientation=orientation,
   2895                       rwidth=rwidth, log=log, color=color, label=label,
-> 2896                       stacked=stacked, **kwargs)
   2897         draw_if_interactive()
   2898     finally:

/usr/lib/python3/dist-packages/matplotlib/axes/_axes.py in hist(self, x, bins, range, normed, weights, cumulative, bottom, histtype, align, orientation, rwidth, log, color, label, stacked, **kwargs)
   5576         # Massage 'x' for processing.
   5577         # NOTE: Be sure any changes here is also done below to 'weights'
-> 5578         if isinstance(x, np.ndarray) or not iterable(x[0]):
   5579             # TODO: support masked arrays;
   5580             x = np.asarray(x)

/usr/local/lib/python3.4/dist-packages/pandas/core/series.py in __getitem__(self, key)
    599         key = com._apply_if_callable(key, self)
    600         try:
--> 601             result = self.index.get_value(self, key)
    602
    603             if not is_scalar(result):

/usr/local/lib/python3.4/dist-packages/pandas/indexes/base.py in get_value(self, series, key)
   2167         try:
   2168             return self._engine.get_value(s, k,
-> 2169                                           tz=getattr(series.dtype, 'tz', None))
   2170         except KeyError as e1:
   2171             if len(self) > 0 and self.inferred_type in ['integer', 'boolean']:

pandas/index.pyx in pandas.index.IndexEngine.get_value (pandas/index.c:3342)()

pandas/index.pyx in pandas.index.IndexEngine.get_value (pandas/index.c:3045)()

pandas/index.pyx in pandas.index.IndexEngine.get_loc (pandas/index.c:4028)()

pandas/src/hashtable_class_helper.pxi in pandas.hashtable.Int64HashTable.get_item (pandas/hashtable.c:8146)()

pandas/src/hashtable_class_helper.pxi in pandas.hashtable.Int64HashTable.get_item (pandas/hashtable.c:8090)()

KeyError: 0

我做了另一次尝试，A为[1,2,None,4]，这很好用。如果索引hist不在0中，那么df['A']是否无法正常工作？

绘制过滤的数据帧

0 个答案: