随机排列numpy数组中的某些行

Question

我只想打乱 numpy 数组中某些行的顺序。这些行将始终是连续的（例如，洗牌第 23-80 行）。每行中的元素数可以从 1（这样数组实际上是 1D）到 100 不等。

下面的示例代码演示了我如何看待方法 shuffle_rows() 的工作原理。我将如何设计这样一种方法来有效地进行这种改组？

import numpy as np
>>> a = np.arange(20).reshape(4, 5)
>>> a
array([[ 0,  1,  2,  3,  4],
       [ 5,  6,  7,  8,  9],
       [10, 11, 12, 13, 14],
       [15, 16, 17, 18, 19]])

>>> shuffle_rows(a, [1, 3]) # including rows 1, 2 and 3 in the shuffling
array([[ 0,  1,  2,  3,  4],
       [15, 16, 17, 18, 19],
       [ 5,  6,  7,  8,  9],
       [10, 11, 12, 13, 14]])

Answer 1

您可以使用 np.random.shuffle。这会打乱行本身，而不是行中的元素。

来自docs：

This function only shuffles the array along the first index of a multi-dimensional array

举个例子：

import numpy as np


def shuffle_rows(arr,rows):
    np.random.shuffle(arr[rows[0]:rows[1]+1])

a = np.arange(20).reshape(4, 5)

print(a)
# array([[ 0,  1,  2,  3,  4],
#        [ 5,  6,  7,  8,  9],
#        [10, 11, 12, 13, 14],
#        [15, 16, 17, 18, 19]])

shuffle_rows(a,[1,3])

print(a)
#array([[ 0,  1,  2,  3,  4],
#       [10, 11, 12, 13, 14],
#       [15, 16, 17, 18, 19],
#       [ 5,  6,  7,  8,  9]])

shuffle_rows(a,[1,3])

print(a)
#array([[ 0,  1,  2,  3,  4],
#       [10, 11, 12, 13, 14],
#       [ 5,  6,  7,  8,  9],
#       [15, 16, 17, 18, 19]])

随机排列numpy数组中的某些行

Shuffle ordering of some rows in numpy array

python

arrays

numpy

shuffle