Python把二维数组拆分为三维数组，把三维数组拆为四维数组

一时失言乱红尘 2023-02-13 11:04 15阅读 0赞

说实话，我也奇怪我怎么会有这么奇怪的需求，，，

# 把二维数组拆分为三维数组 #

目标：把一个 m ∗ n m\*n m∗n的数组，每x行为一页（x可被m整除），拆分为一个m行n列x页的三维数组

代码

import numpy as np
    a = np.arange(30)
    a.resize(6,5)
    a
    array([[ 0,  1,  2,  3,  4],
           [ 5,  6,  7,  8,  9],
           [10, 11, 12, 13, 14],
           [15, 16, 17, 18, 19],
           [20, 21, 22, 23, 24],
           [25, 26, 27, 28, 29]])
    a.reshape(3,2,5) # 3页，2行，5列
    array([[[ 0,  1,  2,  3,  4],
            [ 5,  6,  7,  8,  9]],
           [[10, 11, 12, 13, 14],
            [15, 16, 17, 18, 19]],
           [[20, 21, 22, 23, 24],
            [25, 26, 27, 28, 29]]])

# 把三维数组拆为四维数组 #

a=np.arange(60)
    a.resize(6,2,5)
    a
    array([[[ 0,  1,  2,  3,  4],
            [ 5,  6,  7,  8,  9]],
           [[10, 11, 12, 13, 14],
            [15, 16, 17, 18, 19]],
           [[20, 21, 22, 23, 24],
            [25, 26, 27, 28, 29]],
           [[30, 31, 32, 33, 34],
            [35, 36, 37, 38, 39]],
           [[40, 41, 42, 43, 44],
            [45, 46, 47, 48, 49]],
           [[50, 51, 52, 53, 54],
            [55, 56, 57, 58, 59]]])
    a.resize(3, 2, 2, 5)
    a
    array([[[[ 0,  1,  2,  3,  4],
             [ 5,  6,  7,  8,  9]],
            [[10, 11, 12, 13, 14],
             [15, 16, 17, 18, 19]]],
           [[[20, 21, 22, 23, 24],
             [25, 26, 27, 28, 29]],
            [[30, 31, 32, 33, 34],
             [35, 36, 37, 38, 39]]],
           [[[40, 41, 42, 43, 44],
             [45, 46, 47, 48, 49]],
            [[50, 51, 52, 53, 54],
             [55, 56, 57, 58, 59]]]])

a从6页2行5列，被拆为3部分2页2行5列，可以看到直接用resize把待拆分数组的第一维直接因子分解，得到的拆分结果不会乱序。

如果对得到的四维数组转置，比如把第二维和第三维换了

a.transpose(0, 2, 1, 3)
    array([[[[ 0,  1,  2,  3,  4],
             [10, 11, 12, 13, 14]],
            [[ 5,  6,  7,  8,  9],
             [15, 16, 17, 18, 19]]],
           [[[20, 21, 22, 23, 24],
             [30, 31, 32, 33, 34]],
            [[25, 26, 27, 28, 29],
             [35, 36, 37, 38, 39]]],
           [[[40, 41, 42, 43, 44],
             [50, 51, 52, 53, 54]],
            [[45, 46, 47, 48, 49],
             [55, 56, 57, 58, 59]]]])

注意`a.transpose(0, 2, 1, 3)`并不会概念a,如果要把转置得到的矩阵存下来就必须赋值，如`b=a.transpose(0, 2, 1, 3)`,这样b就是转置后的矩阵，a并未变化。

b=numpy.array([[1,2],[3,4]])
    c=b.transpose(1,0)
    b
    Out[16]: 
    array([[1, 2],
           [3, 4]])
    c
    Out[17]: 
    array([[1, 3],
           [2, 4]])