split() 数据的 Python 直方图

Question

我正在尝试对包含 float 的文本文件制作直方图:

import matplotlib.pyplot as plt

c1_file = open('densEst1.txt','r')
c1_data =  c1_file.read().split()    
c1_sum = float(c1_data.__len__())

plt.hist(c1_data)
plt.show()

c1_data.__len__() 的输出工作正常，但 hist() 抛出:

C:\Python27\python.exe "C:/x.py"
Traceback (most recent call last):
  File "C:/x.py", line 7, in <module>
    plt.hist(c1_data)
  File "C:\Python27\lib\site-packages\matplotlib\pyplot.py", line 2958, in hist
    stacked=stacked, data=data, **kwargs)
  File "C:\Python27\lib\site-packages\matplotlib\__init__.py", line 1812, in inner
    return func(ax, *args, **kwargs)
  File "C:\Python27\lib\site-packages\matplotlib\axes\_axes.py", line 5995, in hist
    if len(xi) > 0:
TypeError: len() of unsized object

Answer 1

plt.hist 调用失败的主要原因是参数 c1_data 是一个包含字符串的列表。当您打开 一个文件并阅读 它时the result will be a string包含文件内容:

To read a file’s contents, call f.read(size), which reads some quantity of data and returns it as a string (in text mode) or bytes object (in binary mode).

强调我的。

当你现在split这个长字符串你会得到一个包含字符串的列表:

Return a list of the words in the string, using sep as the delimiter string.

然而，字符串列表不是 plt.hist 的有效输入:

>>> import matplotlib.pyplot as plt
>>> plt.hist(['1', '2'])
---------------------------------------------------------------------------
TypeError                                 Traceback (most recent call last)
      1 import matplotlib.pyplot as plt
----> 2 plt.hist(['1', '2'])

C:\...\lib\site-packages\matplotlib\pyplot.py in hist(x, bins, range, normed, weights, cumulative, bottom, histtype, align, orientation, rwidth, log, color, label, stacked, hold, data, **kwargs)
   3079                       histtype=histtype, align=align, orientation=orientation,
   3080                       rwidth=rwidth, log=log, color=color, label=label,
-> 3081                       stacked=stacked, data=data, **kwargs)
   3082     finally:
   3083         ax._hold = washold

C:\...\lib\site-packages\matplotlib\__init__.py in inner(ax, *args, **kwargs)
   1895                     warnings.warn(msg % (label_namer, func.__name__),
   1896                                   RuntimeWarning, stacklevel=2)
-> 1897             return func(ax, *args, **kwargs)
   1898         pre_doc = inner.__doc__
   1899         if pre_doc is None:

C:\...\lib\site-packages\matplotlib\axes\_axes.py in hist(***failed resolving arguments***)
   6178             xmax = -np.inf
   6179             for xi in x:
-> 6180                 if len(xi) > 0:
   6181                     xmin = min(xmin, xi.min())
   6182                     xmax = max(xmax, xi.max())

TypeError: len() of unsized object

解决方案:

您可以简单地将其转换为 float 组:

>>> import numpy as np
>>> plt.hist(np.array(c1_data, dtype=float))