numpy argsort，基于另一个排序列

Question

我想根据第一列对数组 a 进行排序：

import numpy as np

a = np.array([[  1.50000000e+03,   1.68693009e-01],
   [  5.00000000e+02,   1.26512097e-01],
   [  1.50000000e+03,   1.68338907e-01],
   [  5.00000000e+02,   1.22073944e-01],
   [  5.00000000e+02,   1.31257631e-01],
   [  1.50000000e+03,   1.72864036e-01],
   [  1.50000000e+03,   1.70665459e-01],
   [  5.00000000e+02,   1.32951654e-01],
   [  1.00000000e+03,   1.49342105e-01]])
sort = a.T.argsort(0)
b = a[sort]
print(b)

给我：

[[[  5.00000000e+02   1.26512097e-01]
[  5.00000000e+02   1.26512097e-01]
[  5.00000000e+02   1.26512097e-01]
[  5.00000000e+02   1.26512097e-01]
[  5.00000000e+02   1.26512097e-01]
[  5.00000000e+02   1.26512097e-01]
[  5.00000000e+02   1.26512097e-01]
[  5.00000000e+02   1.26512097e-01]
[  5.00000000e+02   1.26512097e-01]]

[[  1.50000000e+03   1.68693009e-01]
[  1.50000000e+03   1.68693009e-01]
[  1.50000000e+03   1.68693009e-01]
[  1.50000000e+03   1.68693009e-01]
[  1.50000000e+03   1.68693009e-01]
[  1.50000000e+03   1.68693009e-01]
[  1.50000000e+03   1.68693009e-01]
[  1.50000000e+03   1.68693009e-01]
[  1.50000000e+03   1.68693009e-01]]]

我的条目在哪里 a[:,0] == 1000？它消失了。我如何生成一个数组，如 a_sorted[0] = sorted x 和 a_sorted[1] = sorted y？

如果我不在 argsort 之前转置 a，我会得到一个形状为 (9, 2, 2)

的数组

Answer 1

a.sort(0)

根据第一列对数组进行排序（并保留 1000）：

array([[  5.00000000e+02,   1.22073944e-01],
       [  5.00000000e+02,   1.26512097e-01],
       [  5.00000000e+02,   1.31257631e-01],
       [  5.00000000e+02,   1.32951654e-01],
       [  1.00000000e+03,   1.49342105e-01],
       [  1.50000000e+03,   1.68338907e-01],
       [  1.50000000e+03,   1.68693009e-01],
       [  1.50000000e+03,   1.70665459e-01],
       [  1.50000000e+03,   1.72864036e-01]])

如果不想就地排序，可以使用：

a[a.argsort(0)[:,0]]

numpy argsort，基于另一个排序列

numpys argsort, sorting column based on another one

python

numpy