[英]Permuting entire rows in a 2d numpy array
Consider numpy array arr
, shown below:考虑 numpy 数组arr
,如下所示:
arr = ([[1, 5, 6, 3, 3, 7],
[2, 2, 2, 2, 2, 2],
[0, 1, 0, 1, 0, 1],
[4, 8, 4, 8, 4, 8],
[1, 2, 3, 4, 5, 6]])
I want to find all row permutations of arr
.我想找到arr
的所有行排列。 NOTE: the order of elements in any given row is unchanged.注意:任何给定行中元素的顺序是不变的。 It is the entire rows that are being permuted.正在排列的是整行。
Because arr
has 5 rows, there will be 5. = 120 permutations.因为arr
有5行,所以会有5.=120个排列。 I'm hoping these could be 'stacked' into a 3d array p
, having shape (120, 5, 6):我希望这些可以“堆叠”到 3d 数组p
中,形状为 (120, 5, 6):
p = [[[1, 5, 6, 3, 3, 7],
[2, 2, 2, 2, 2, 2],
[0, 1, 0, 1, 0, 1],
[4, 8, 4, 8, 4, 8],
[1, 2, 3, 4, 5, 6]],
[[1, 5, 6, 3, 3, 7],
[2, 2, 2, 2, 2, 2],
[0, 1, 0, 1, 0, 1],
[1, 2, 3, 4, 5, 6]
[4, 8, 4, 8, 4, 8]],
… etc …
[[1, 2, 3, 4, 5, 6],
[4, 8, 4, 8, 4, 8],
[0, 1, 0, 1, 0, 1],
[2, 2, 2, 2, 2, 2],
[1, 5, 6, 3, 3, 7]]]
There is a lot of material online about permitting elements within rows, but I need help in permuting the entire rows themselves.网上有很多关于行内允许元素的资料,但我需要帮助自己排列整行。
You can make use of itertools.permutations
and np.argsort
:您可以使用itertools.permutations
和np.argsort
:
from itertools import permutations
out = np.array([arr[np.argsort(idx)] for idx in permutations(range(5))])
print(out)
[[[1 5 6 3 3 7]
[2 2 2 2 2 2]
[0 1 0 1 0 1]
[4 8 4 8 4 8]
[1 2 3 4 5 6]]
[[1 5 6 3 3 7]
[2 2 2 2 2 2]
[0 1 0 1 0 1]
[1 2 3 4 5 6]
[4 8 4 8 4 8]]
[[1 5 6 3 3 7]
[2 2 2 2 2 2]
[4 8 4 8 4 8]
[0 1 0 1 0 1]
[1 2 3 4 5 6]]
...
[[1 2 3 4 5 6]
[0 1 0 1 0 1]
[4 8 4 8 4 8]
[2 2 2 2 2 2]
[1 5 6 3 3 7]]
[[4 8 4 8 4 8]
[1 2 3 4 5 6]
[0 1 0 1 0 1]
[2 2 2 2 2 2]
[1 5 6 3 3 7]]
[[1 2 3 4 5 6]
[4 8 4 8 4 8]
[0 1 0 1 0 1]
[2 2 2 2 2 2]
[1 5 6 3 3 7]]]
Similar answer, but you do not need to.argsort one more time类似的答案,但您不需要再进行一次 .argsort
from itertools import permutations
import numpy as np
arr = np.array([[1, 5, 6, 3, 3, 7],
[2, 2, 2, 2, 2, 2],
[0, 1, 0, 1, 0, 1],
[4, 8, 4, 8, 4, 8],
[1, 2, 3, 4, 5, 6]])
output = np.array([arr[i, :] for i in permutations(range(5))])
print(output)
[[[1 5 6 3 3 7]
[2 2 2 2 2 2]
[0 1 0 1 0 1]
[4 8 4 8 4 8]
[1 2 3 4 5 6]]
[[1 5 6 3 3 7]
[2 2 2 2 2 2]
[0 1 0 1 0 1]
[1 2 3 4 5 6]
[4 8 4 8 4 8]]
[[1 5 6 3 3 7]
[2 2 2 2 2 2]
[4 8 4 8 4 8]
[0 1 0 1 0 1]
[1 2 3 4 5 6]]
...
[[1 2 3 4 5 6]
[4 8 4 8 4 8]
[2 2 2 2 2 2]
[0 1 0 1 0 1]
[1 5 6 3 3 7]]
[[1 2 3 4 5 6]
[4 8 4 8 4 8]
[0 1 0 1 0 1]
[1 5 6 3 3 7]
[2 2 2 2 2 2]]
[[1 2 3 4 5 6]
[4 8 4 8 4 8]
[0 1 0 1 0 1]
[2 2 2 2 2 2]
[1 5 6 3 3 7]]]
This is a bit faster, here are speed comparisons:这样比较快一些,下面是速度对比:
%%timeit
output = np.array([arr[i, :] for i in permutations(range(5))])
381 µs ± 14.9 µs per loop (mean ± std. dev. of 7 runs, 1,000 loops each)
%%timeit
output = np.array([arr[np.argsort(idx)] for idx in permutations(range(5))])
863 µs ± 97.7 µs per loop (mean ± std. dev. of 7 runs, 1,000 loops each)
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