如果该列中的所有元素均满足条件，则删除该多维数组中的一列 [英] Delete a column in a multi-dimensional array if all elements in that column satisfy a condition

问题描述

我有一个多维数组，例如；

I have a multi-dimensional array such as;

a = [[1,1,5,12,0,4,0],
     [0,1,2,11,0,4,2],
     [0,4,3,17,0,4,9],
     [1,3,5,74,0,8,16]]

如何删除如果该列中的所有条目都等于零？在数组a中，这意味着删除第4列，结果是：

How can I delete the column if all entries within that column are equal to zero? In the array a that would mean deleting the 4th column resulting in:

 a = [[1,1,5,12,4,0],
     [0,1,2,11,4,2],
     [0,4,3,17,4,9],
     [1,3,5,74,8,16]]

Nb我已将a编写为嵌套列表，但仅讲清楚我也不知道数组中零列的先验位置。

N.b I've written a as a nested list but only to make it clear. I also don't know a priori where the zero column will be in the array.

到目前为止，我的尝试只是找到所有元素均相等的列的索引归零：

My attempt so far only finds the index of the column in which all elements are equal to zero:

a = np.array([[1,1,5,12,0,4,0],[0,1,2,11,0,4,2],[0,4,3,17,0,4,9],[1,3,5,74,0,8,16]])
b = np.vstack(a)
ind = []
for n,m in zip(b.T,range(len(b.T))):
    if sum(n) == 0:
       ind.append(m)

有什么方法可以实现？

Is there any way to achieve this?

推荐答案

使用已经拥有的代码，您可以执行以下操作：

With the code you already have, you can just do:

for place in ind:
    for sublist in a:
        del sublist[place]

哪个工作完成了，但不是很令人满意...

Which gets the job done but is not very satisfactory...

编辑：numpy强大

import numpy as np
a = np.array(a)
a = a[:, np.sum(a, axis=0)!=0]

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