9月19日总结
匹配/广播机制
DataFrame 支持 add()
(opens new window)、sub()
(opens new window)、mul()
(opens new window)、div()
(opens new window)及 radd()
(opens new window)、rsub()
(opens new window)等方法执行二进制操作。广播机制重点关注输入的 Series。通过 axis
关键字,匹配 index 或 columns 即可调用这些函数。
In [18]: df = pd.DataFrame({
....: 'one': pd.Series(np.random.randn(3), index=['a', 'b', 'c']),
....: 'two': pd.Series(np.random.randn(4), index=['a', 'b', 'c', 'd']),
....: 'three': pd.Series(np.random.randn(3), index=['b', 'c', 'd'])})
....:
In [19]: df
Out[19]:
one two three
a 1.394981 1.772517 NaN
b 0.343054 1.912123 -0.050390
c 0.695246 1.478369 1.227435
d NaN 0.279344 -0.613172
In [20]: row = df.iloc[1]
In [21]: column = df['two']
In [22]: df.sub(row, axis='columns')
Out[22]:
one two three
a 1.051928 -0.139606 NaN
b 0.000000 0.000000 0.000000
c 0.352192 -0.433754 1.277825
d NaN -1.632779 -0.562782
In [23]: df.sub(row, axis=1)
Out[23]:
one two three
a 1.051928 -0.139606 NaN
b 0.000000 0.000000 0.000000
c 0.352192 -0.433754 1.277825
d NaN -1.632779 -0.562782
In [24]: df.sub(column, axis='index')
Out[24]:
one two three
a -0.377535 0.0 NaN
b -1.569069 0.0 -1.962513
c -0.783123 0.0 -0.250933
d NaN 0.0 -0.892516
In [25]: df.sub(column, axis=0)
Out[25]:
one two three
a -0.377535 0.0 NaN
b -1.569069 0.0 -1.962513
c -0.783123 0.0 -0.250933
d NaN 0.0 -