python - 如何删除 numpy.array 中的列

Question

我想删除 numpy.array 中的选定列。我就是这样做的:

n [397]: a = array([[ NaN,   2.,   3., NaN],
   .....:        [  1.,   2.,   3., 9]])

In [398]: print a
[[ NaN   2.   3.  NaN]
 [  1.   2.   3.   9.]]

In [399]: z = any(isnan(a), axis=0)

In [400]: print z
[ True False False  True]

In [401]: delete(a, z, axis = 1)
Out[401]:
 array([[  3.,  NaN],
       [  3.,   9.]])

在此示例中，我的目标是删除所有包含 NaN 的列。我期待最后一个命令 结果:

array([[2., 3.],
       [2., 3.]])

我该怎么做？

Answer 1

鉴于它的名字，我认为标准的方式应该是delete:

import numpy as np

A = np.delete(A, 1, 0)  # delete second row of A
B = np.delete(B, 2, 0)  # delete third row of B
C = np.delete(C, 1, 1)  # delete second column of C

根据numpy's documentation page ，numpy.delete的参数如下:

numpy.delete(arr, obj, axis=None)

• arr 指的是输入数组，
• obj 指的是哪些子数组(例如列/行号或数组的切片)和
• axis 指的是按列(axis = 1)或按行(axis = 0)删除操作。