Python numpy 在给定位置将二维数组插入更大的二维数组

Question

假设您有一个 Numpy 二维数组：

import numpy as np

big = np.zeros((4, 4))
>>> big
array([[0., 0., 0., 0.],
       [0., 0., 0., 0.],
       [0., 0., 0., 0.],
       [0., 0., 0., 0.]])

另一个二维数组，两个轴的长度小于或等于：

small = np.array([
    [1, 2],
    [3, 4]
])

您现在想要用 small 的值覆盖 big 的某些值，从 small 的左上角开始 -> small[0][0]指向 big.

例如：

import numpy as np

big = np.zeros((4, 4))

small = np.array([
    [1, 2],
    [3, 4]
])

def insert_at(big_arr, pos, to_insert_arr):
    return [...]


result = insert_at(big, (1, 2), small)

>>> result
array([[0., 0., 0., 0.],
       [0., 0., 1., 2.],
       [0., 0., 3., 4.],
       [0., 0., 0., 0.]])

我期待一个 numpy 函数，但找不到。

Answer 1

为此，

确保位置不会使小矩阵超出大矩阵的边界
把大矩阵的部分在小矩阵的位置进行子集

import numpy as np

big = np.zeros((4, 4))

small = np.array([
    [1, 2],
    [3, 4]
])

def insert_at(big_arr, pos, to_insert_arr):
    x1 = pos[0]
    y1 = pos[1]
    x2 = x1 + small.shape[0]
    y2 = y1 + small.shape[1]

    assert x2  <= big.shape[0], "the position will make the small matrix exceed the boundaries at x"
    assert y2  <= big.shape[1], "the position will make the small matrix exceed the boundaries at y"

    big[x1:x2,y1:y2] = small

    return big
    


result = insert_at(big, (1, 2), small)
result

Python numpy 在给定位置将二维数组插入更大的二维数组

Python numpy insert 2d array into bigger 2d array on given posiiton

python

arrays

numpy

multidimensional-array

insertion