Python 尝试在matplotlib中打印或删除数据时出现KeyError

从导入的csv文件生成基本分布直方图时遇到问题。该代码适用于来自另一个csv的一组数据，但不是我感兴趣的，本质上是相同的。以下是我尝试过的代码：

import pandas as pd
import numpy as np
import matplotlib as plt
data = pd.read_csv("idcases.csv")
data1 = data[(data["Disease"] == "Amebiasis") & (data["County"] == "Marin")]
data2 = data[(data["Disease"] == "Amebiasis") & (data["County"] == "Sonoma")]

fig = plt.pyplot.figure()
ax = fig.add_subplot(111)
ax.hist(data1['Population'], bins =10, range = (data1['Population'].min(), data1['Population'].max()))
plt.pyplot.xlabel('Population')
plt.pyplot.ylabel('Count of Population')
plt.pyplot.show()

这将产生：

---------------------------------------------------------------------------
KeyError                                  Traceback (most recent call last)
<ipython-input-35-63303aa9d8a5> in <module>()
      1 fig = plt.pyplot.figure()
      2 ax = fig.add_subplot(111)
----> 3 ax.hist(data1['Population'], bins =10, range = (data1['Population'].min(), data1['Population'].max()))
  4 plt.pyplot.xlabel('Count')
  5 plt.pyplot.ylabel('Count of Population')

C:\Program Files (x86)\Anaconda\lib\site-packages\matplotlib\axes\_axes.py in hist(self, x, bins, range, normed, weights, cumulative, bottom, histtype, align, orientation, rwidth, log, color, label, stacked, **kwargs)
   5602         # Massage 'x' for processing.
   5603         # NOTE: Be sure any changes here is also done below to 'weights'
-> 5604         if isinstance(x, np.ndarray) or not iterable(x[0]):
   5605             # TODO: support masked arrays;
   5606             x = np.asarray(x)

C:\Program Files (x86)\Anaconda\lib\site-packages\pandas\core\series.py in __getitem__(self, key)
    549     def __getitem__(self, key):
    550         try:
--> 551             result = self.index.get_value(self, key)
    552 
    553             if not np.isscalar(result):

C:\Program Files (x86)\Anaconda\lib\site-packages\pandas\core\index.py in get_value(self, series, key)
   1721 
   1722         try:
-> 1723             return self._engine.get_value(s, k)
   1724         except KeyError as e1:
   1725             if len(self) > 0 and self.inferred_type in ['integer','boolean']:

pandas\index.pyx in pandas.index.IndexEngine.get_value (pandas\index.c:3204)()

pandas\index.pyx in pandas.index.IndexEngine.get_value (pandas\index.c:2903)()

pandas\index.pyx in pandas.index.IndexEngine.get_loc (pandas\index.c:3843)()

pandas\hashtable.pyx in pandas.hashtable.Int64HashTable.get_item (pandas\hashtable.c:6525)()

pandas\hashtable.pyx in pandas.hashtable.Int64HashTable.get_item (pandas\hashtable.c:6463)()

KeyError: 0L

对我来说：

import io
import matplotlib.pyplot as plt


s = """       Disease County  Year     Sex  Count  Population   Rate  CI.lower
 Amebiasis  Marin  2001   Total     14      247731  5.651     3.090   
 Amebiasis  Marin  2001  Female      0      125414  0.000     0.000   
Amebiasis  Marin  2001    Male      0      122317  0.000     0.000   
Amebiasis  Marin  2002   Total      7      247382  2.830     1.138   
Amebiasis  Marin  2002  Female      0      125308  0.000     0.000   
 Amebiasis  Marin  2002    Male      0      122074  0.000     0.000   
Amebiasis  Marin  2003   Total      9      247280  3.640     1.664   
Amebiasis  Marin  2003  Female      0      125259  0.000     0.000   
 Amebiasis  Marin  2003    Male      0      122021  0.000     0.000  """
fobj = io.StringIO(s)
data1 = pd.read_csv(fobj, delim_whitespace=True)
plt.hist(data1['Population'], bins =10, range = (data1['Population'].min(), data1['Population'].max()))
plt.xlabel('Population')
plt.ylabel('Count of Population')
plt.show()

---

在从

matploblib-v1.4.3

升级到

matplotlib-v1.5.0

时，我注意到

pandas.Series

的绘图停止工作，例如：

ax.plot_date(df['date'], df['raw'], '.-', label='raw')

将导致

键错误：0

异常

快速解决方案： 您需要将

numpy.ndarray

而不是

pandas.Series

传递到

plot\u date

函数：

ax.plot_date(df['date'].values, df['raw'].values, '.-', label='raw')

更多详情： 让我们看一下异常的完整回溯：

# ... PREVIOUS TRACEBACK MESSAGES OMITTED FOR BREVITY ...

C:\Users\pedromdu\AppData\Local\Continuum\Anaconda3\lib\site-packages\matplotlib\dates.py in default_units(x, axis)
   1562 
   1563         try:
-> 1564             x = x[0]
   1565         except (TypeError, IndexError):
   1566             pass

C:\Users\pedromdu\AppData\Local\Continuum\Anaconda3\lib\site-packages\pandas\core\series.py in __getitem__(self, key)
    555     def __getitem__(self, key):
    556         try:
--> 557             result = self.index.get_value(self, key)
    558 
    559             if not np.isscalar(result):

C:\Users\pedromdu\AppData\Local\Continuum\Anaconda3\lib\site-packages\pandas\core\index.py in get_value(self, series, key)
   1788 
   1789         try:
-> 1790             return self._engine.get_value(s, k)
   1791         except KeyError as e1:
   1792             if len(self) > 0 and self.inferred_type in ['integer','boolean']:

pandas\index.pyx in pandas.index.IndexEngine.get_value (pandas\index.c:3204)()

pandas\index.pyx in pandas.index.IndexEngine.get_value (pandas\index.c:2903)()

pandas\index.pyx in pandas.index.IndexEngine.get_loc (pandas\index.c:3843)()

pandas\hashtable.pyx in pandas.hashtable.Int64HashTable.get_item (pandas\hashtable.c:6525)()

pandas\hashtable.pyx in pandas.hashtable.Int64HashTable.get_item (pandas\hashtable.c:6463)()

KeyError: 0

请注意，当matploblib尝试执行

x=x[0]

时，会产生错误。如果熊猫系列未使用从零开始的整数编制索引，这将失败，因为这将查找索引值为

0

的项目，而不是

pandas.series

的

0th

元素

要解决此问题，我们需要从熊猫系列中的数据中获得一个

numpy.ndarray

，然后使用该数据进行绘图：

ax.plot_date(df['date'].values, df['raw'].values, '.-', label='raw')

---

这就是熊猫的问题。请显示

data1

的内容。您粘贴的数据似乎是以制表符分隔的（或粘贴后格式化的）。确保所有csv文件都有相同的分隔符，并将其作为参数提供给read_csvfunction@MikeMüller，数据1的内容在最后。@hitzg，我在粘贴后进行了格式化，以便更好地查看。我怎样才能知道使用了哪个分离器？csv文件本质上不都是逗号吗？

ax.plot_date(df['date'].values, df['raw'].values, '.-', label='raw')