通过使用 NumPy 对 2 个数组元素数组进行求和来形成矩阵

2022-01-09 00:00:00 python numpy arrays sum

问题描述

假设我有以下 NumPy 数组:

Let's say I have the following NumPy arrays:

i = array([2, 4, 5])
j = array([0, 1, 2])

我希望有一个非常有效的方法(如果可能，内置)来对这些向量求和，并得到如下所示的输出:

I would like to have a very efficient method (built-in if possible) to sum those vectors and have an output that looks like this:

[[2 4 5]
 [3 5 6]
 [4 6 7]]

所以基本上每一列都是数组 j，其中 i 的第 k 个元素已添加到其中(在本例中为 k = 0, 1, 2)

So basically each column is the array j to which the k th element of i has been added (k = 0, 1, 2 in this case)

解决方案

使用 numpy.add.outer.

>>> import numpy as np                                                                                                 
>>> i = np.array([2, 4, 5])                                                                                            
>>> j = np.array([0, 1, 2])                                                                                            
>>>                                                                                                                    
>>> np.add.outer(j, i)                                                                                                 
array([[2, 4, 5],
       [3, 5, 6],
       [4, 6, 7]])

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