Question

我的程序导入了这些：

import requests
import demjson

import pandas as pd
from pandas import DataFrame

import pylab
pylab.show()

我有一个数据框，如果我打印出来就像这样：

    Strike    COI    POI
0    50.00    927   1694
1    55.00    394   1898
2    60.00   2042   4438
3    65.00    642   3696
4    70.00   3169   3216
5    75.00   2529   3222
6    80.00   6268  14029
7    85.00   3988   6241
8    87.50    356   1516
9    90.00  15676  14345
10   92.50   1309   2498
11   95.00   3303  11391
12   97.50   1074   1472
13  100.00  64930  19513
14  105.00  10953   9286
15  110.00  19956  13008
16  115.00  13956  12932
17  120.00  23440   9240
18  125.00  12167   7467
19  130.00  23531  10168
20  135.00   9567   2637
21  140.00  18967   6854
22  145.00   7890   5176
23  150.00  21516   8079
24  155.00   3137    267
25  160.00   4115    432
26  165.00   1079    205
27  170.00   4341    785
28  175.00   6277   1631
29  180.00   1805     35
30  185.00    906    136
31  190.00   1984    377
32  195.00   3539    268

有时会有像这样的零值

    Strike   COI   POI
0    95.00    53   663
1   100.00    16   595
2   105.00     6   377
3   110.00    56  1217
4   115.00   174   994
5   120.00   631  3227
6   125.00   701  1031
7   130.00  2678   833
8   135.00  1921  1049
9   140.00  1238    10
10  160.00  1486     0
11  165.00  1900     0

不幸的是，有时候Strike是这样的浮动：

    Strike    COI    POI
0    34.29    476  12711
1    35.71     95   7782
2    37.14      0   7844
3    38.57      0   3640
4    40.00     93   6010
5    41.43      0   5621
6    42.86   1245  18146
7    44.29    116   6844
8    45.71    140   7099
9    47.14    500    483
10   48.57    445   3956
11   50.00   1540  22362
12   51.43    152   6366
13   52.86    131   8354
14   54.29    810   7542
15   55.71    132   9337
16   57.14  12455  15024
17   58.57    662   5245
18   60.00   1743   9116
19   61.43   1368   7236
20   62.86   1128  11890
21   64.29   4537  24204
22   65.71    766   5113
23   67.14   1859  10572
24   68.57  12407  11367
25   70.00  13263  11748
26   71.43  23400  31566
27   72.86   2784  12984
28   74.29  12679  20520
29   75.71   6932  14617
..     ...    ...    ...
63  115.00  39738  18033
64  115.71   5293   2877
65  116.43   1874   2748
66  117.14   4181   1965
67  117.86   3618   4214
68  118.57  11652   4043
69  120.00  81523  34752
70  121.43  14239   3527
71  122.86   9046   6160
72  125.00    187     88
73  125.71  22557   7381
74  128.57  11053   8163
75  130.00  74007  27825
76  131.43   6747   1951
77  132.86   7289   1383
78  134.29   5872   1380
79  135.71   4946   2047
80  137.14   5349    590
81  140.00  98310  57767
82  145.00   9857    403
83  150.00  64701   2063
84  155.00  17398   1434
85  160.00  12363   1133
86  165.00   5222    539
87  170.00   9050    918
88  175.00   9848    678
89  180.00   3408     85
90  185.00   3243    768
91  190.00   3646    419
92  195.00   4789    149

由于我希望Strikes成为bin，我试图通过说：

绘制直方图

df.hist(by=df.Strike)

但我得不到任何结果，或者当我看到系统准备用一堆小网格绘图时（我正在使用Spyder）我在任何情节之前都会得到这个错误。据我所知，所有数据帧都至少有一个点。 y轴也没有意义，因为它的高度似乎总是一个：

Traceback (most recent call last):

  File "<ipython-input-20-6f27fa6cf56c>", line 1, in <module>
    runfile('/home/idf/goog.py', wdir='/home/idf')

  File "/home/idf/anaconda/lib/python2.7/site-packages/spyderlib/widgets/externalshell/sitecustomize.py", line 682, in runfile
    execfile(filename, namespace)

  File "/home/idf/anaconda/lib/python2.7/site-packages/spyderlib/widgets/externalshell/sitecustomize.py", line 78, in execfile
    builtins.execfile(filename, *where)

  File "/home/idf/goog.py", line 153, in <module>
    df.hist(by=df.Strike)

  File "/home/idf/anaconda/lib/python2.7/site-packages/pandas/tools/plotting.py", line 2740, in hist_frame
    **kwds)

  File "/home/idf/anaconda/lib/python2.7/site-packages/pandas/tools/plotting.py", line 2873, in grouped_hist
    figsize=figsize, layout=layout, rot=rot)

  File "/home/idf/anaconda/lib/python2.7/site-packages/pandas/tools/plotting.py", line 2983, in _grouped_plot
    plotf(group, ax, **kwargs)

  File "/home/idf/anaconda/lib/python2.7/site-packages/pandas/tools/plotting.py", line 2867, in plot_group
    ax.hist(group.dropna().values, bins=bins, **kwargs)

  File "/home/idf/anaconda/lib/python2.7/site-packages/matplotlib/axes/_axes.py", line 5597, in hist
    raise ValueError("x must have at least one data point")

ValueError: x must have at least one data point

Answer 1

当您调用DataFrame.hist方法（即pandas内部绘图功能）时，您只需传递一个列名称：

df.hist('Strike') # which is the same as df.hist(column='Strike')

获得：

enter image description here

如果您使用plt.hist（直接访问matplotlib函数），则需要传递df.Strike.values。

如何绘制直方图

1 个答案: