根据按键阵列重塑 [英] Array reshaped according to keys

问题描述

我不知道什么我希望做确切的技术术语，所以我会试着用一个例子证明：

I don't know the exact technical terms for what I wish to do, so I'll try and demonstrate with an example:

我有两个向量的长度相同，的 A 和乙的，如下：

I have two vectors the same length, a and b, as below:

In [41]:a
Out[41]:
array([ 0.61689215,  0.31368813,  0.47680184, ...,  0.84857976,
    0.97026244,  0.89725481])

In [42]:b
Out[42]:
array([35, 36, 37, ..., 36, 37, 38])

的在的有N个浮​​点数和乙的有n个元素：与10个不同值的键：35，36，37，...，43，44

a contains N floating point numbers and b contains N elements: keys with 10 distinct values: 35, 36, 37, ..., 43, 44

我希望得到一个新的矩阵的 M 的有10列，其中第一列包含的在的所有行的相应键的乙 35是在第二列的 M 的包含所有行的在的，其相应的键的乙的是36等都达列10的 M 的

I wish to get a new matrix M that has 10 columns where the first column contains all the rows in a whose corresponding key in b is 35. The second column in M contains all the rows in a whose corresponding key in b is 36. Etc. all up to column 10 in M.

我希望这是显而易见的。谢谢

I hope this was clear. Thank you

推荐答案

您可以用熊猫：

import numpy as np
import pandas as pd

a = np.random.rand(50)
b = np.random.randint(10, 15, 50)

s = pd.Series(a)
s.groupby(b).apply(pd.Series.reset_index, drop=True).unstack(level=0)

的输出是：

          10        11        12        13        14
0   0.465079  0.041393  0.692856  0.634328  0.179690
1   0.934678  0.746048  0.060014  0.072626  0.824729
2   0.388190  0.510527  0.078662  0.077157  0.291183
3   0.972033  0.761159  0.017317  0.104768  0.278871
4   0.750713  0.430246  0.083407  0.262037  0.487742
5   0.216965  0.482364  0.820535  0.207008  0.276452
6   0.282038  0.607303  0.675856  0.994369  0.602059
7   0.897106  0.398808  0.312332  0.751388  0.878177
8   0.229121       NaN       NaN  0.061288  0.032066
9   0.810678       NaN       NaN       NaN  0.718237
10  0.571125       NaN       NaN       NaN  0.668292
11  0.410750       NaN       NaN       NaN  0.288145
12  0.984507       NaN       NaN       NaN       NaN

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