Question

我正在尝试将某些数组重塑为特定顺序，但是numpy.reshape不能解决我的问题，除非真正需要，否则我不想使用任何循环。

让我们使用一个值为a的数组：

a = [['x1','x2','x3','y1','y2','y3','z1','z2','z3'],
['x4','x5','x6','y4','y5','y6','z4','z5','z6']]

和np.reshape(a,[-1,18])返回：

array([['x1', 'x2', 'x3', 'y1', 'y2', 'y3', 'z1', 'z2', 'z3', 
     'x4', 'x5','x6', 'y4', 'y5', 'y6', 'z4', 'z5', 'z6']], dtype='<U2')

但是有可能得到这样的结果：

[['x1', 'x2', 'x3','x4', 'x5','x6', 'y1', 'y2', 'y3','y4', 'y5', 'y6',
 'z1', 'z2', 'z3', 'z4', 'z5', 'z6']]

Answer 1

您需要key和reshape数组：

import numpy as np

a = np.array([['x1','x2','x3','y1','y2','y3','z1','z2','z3'],
              ['x4','x5','x6','y4','y5','y6','z4','z5','z6']])
b = a.reshape(2, 3, 3).transpose((1, 0, 2)).ravel()
print(b)
# ['x1' 'x2' 'x3' 'x4' 'x5' 'x6' 'y1' 'y2' 'y3' 'y4' 'y5' 'y6' 'z1' 'z2'
#  'z3' 'z4' 'z5' 'z6']

一步一步，首先要有初始数组。

print(a)
# [['x1' 'x2' 'x3' 'y1' 'y2' 'y3' 'z1' 'z2' 'z3']
#  ['x4' 'x5' 'x6' 'y4' 'y5' 'y6' 'z4' 'z5' 'z6']]

然后将其重塑为“两个3x3矩阵”：

print(a.reshape(2, 3, 3))
# [[['x1' 'x2' 'x3']
#   ['y1' 'y2' 'y3']
#   ['z1' 'z2' 'z3']]
#
#  [['x4' 'x5' 'x6']
#   ['y4' 'y5' 'y6']
#   ['z4' 'z5' 'z6']]]

现在，如果您将其展平，则在x3之后，您将得到y1。您需要重新排列轴，以便在x3进入x4之后，这意味着您首先要迭代列（x1，x2，x3），然后跳转到下一个矩阵以迭代其第一行中的列（x4，x5，x6），然后继续到第一矩阵的下一行。因此，最里面的尺寸应该是相同的（列），但是您必须交换前两个尺寸，因此您首先要更改矩阵，然后更改行，而不是相反：

print(a.reshape(2, 3, 3).transpose((1, 0, 2)))
# [[['x1' 'x2' 'x3']
#   ['x4' 'x5' 'x6']]
#
#  [['y1' 'y2' 'y3']
#   ['y4' 'y5' 'y6']]
#
#  [['z1' 'z2' 'z3']
#   ['z4' 'z5' 'z6']]]

现在可以拉平以获得所需的结果。

print(a.reshape(2, 3, 3).transpose((1, 0, 2)).ravel())
# ['x1' 'x2' 'x3' 'x4' 'x5' 'x6' 'y1' 'y2' 'y3' 'y4' 'y5' 'y6' 'z1' 'z2'
#  'z3' 'z4' 'z5' 'z6']

Answer 2

如果x，y和z的长度相同，则可以使用np.array_split并用.ravel()展平结果：< / p>

np.array(np.array_split(a, 3, axis=1)).ravel()

array(['x1', 'x2', 'x3', 'x4', 'x5', 'x6', 'y1', 'y2', 'y3', 'y4', 'y5',
       'y6', 'z1', 'z2', 'z3', 'z4', 'z5', 'z6'], dtype='<U2')

如何用特定的索引顺序重塑numpy数组？

2 个答案: