用numpy数组替换pandas数据帧变量值

Question

我正在对pandas数据框中的变量进行转换,然后我想用新值替换该列.问题似乎是在转换之后,数组的长度与我的数据帧索引的长度不同.我不认为这是真的.

>>> df['variable'] = stats.boxcox(df.variable)
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "C:\Users\eMachine\WinPython-64bit-2.7.5.3\python-2.7.5.amd64\lib\site-packages\pandas\core\frame.py", line 2119, in __setitem__
    self._set_item(key, value)
  File "C:\Users\eMachine\WinPython-64bit-2.7.5.3\python-2.7.5.amd64\lib\site-packages\pandas\core\frame.py", line 2165, in _set_item
    value = self._sanitize_column(key, value)
  File "C:\Users\eMachine\WinPython-64bit-2.7.5.3\python-2.7.5.amd64\lib\site-packages\pandas\core\frame.py", line 2205, in _sanitize_column
    raise AssertionError('Length of values does not match '
AssertionError: Length of values does not match length of index

当我检查长度时,这些长度似乎不一致.len(数组)说它是2但是当我打电话给stats.boxcox它说它是50000.这里发生了什么？

>>> len(df)
50000
>>> len(stats.boxcox(df.variable))
2
>>> stats.boxcox(df.variable)
(0    -0.079496
1    -0.117982
2    -0.104637

...
49985    -0.041300
49986     0.651771
49987    -0.115660
49988    -0.118034
49998    -0.118014
49999    -0.034076
Name: feat9, Length: 50000, dtype: float64, 8.4721358117221772)
>>> 

Answer 1

您可以在示例中看到结果boxcox是元组.这与文档一致,表明boxcox返回转换数据的元组和lambda值.请注意该页面上的示例:

xt, _ = stats.boxcox(x)

...再次显示boxcox返回2元组.

你应该这样做df['variable'] = stats.boxcox(df.variable)[0].