按字典顺序排序2d numpy数组

问题描述

我有一个大型的二维数组，其中包含数百列.我想按字典顺序对其进行排序，即按第一列，然后按第二列，依此类推，直到最后一列.我想这应该很容易做到，但是我还没有找到一种快速的方法.

I have a large 2d array with hundreds of columns. I would like to sort it lexicographically, i.e. by first column, then by second column, and so on until the last column. I imagine this should be easy to do but I haven't been able to find a quick way to do this.

推荐答案

这是 numpy.lexsort 用于，但界面很尴尬.将其传递给2D数组，它将对列进行argsort排序，首先按 last 行排序，然后按倒数第二行进行，直到第一行:

This is what numpy.lexsort is for, but the interface is awkward. Pass it a 2D array, and it will argsort the columns, sorting by the last row first, then the second-to-last row, continuing up to the first row:

>>> x
array([[0, 0, 0, 2, 3],
       [2, 3, 2, 3, 2],
       [3, 1, 3, 0, 0],
       [3, 1, 1, 3, 1]])
>>> numpy.lexsort(x)
array([4, 1, 2, 3, 0], dtype=int64)

如果要按行排序，并以第一列为主键，则需要先旋转数组，然后再lexsort对其进行操作:

If you want to sort by rows, with the first column as the primary key, you need to rotate the array before lexsorting it:

>>> x[numpy.lexsort(numpy.rot90(x))]
array([[0, 0, 0, 2, 3],
       [2, 3, 2, 3, 2],
       [3, 1, 1, 3, 1],
       [3, 1, 3, 0, 0]])

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