Sorting the order of entire columns in numpy

StackOverflow https://stackoverflow.com/questions/23616729

  •  21-07-2023
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문제

How can I sort this 3,20 ndarray by column? The np.sort() doesnt seem to do what I think it does. I want to turn this:

                                                                 a
array([[0, 0, 0, 0, 1, 1, 1, 2, 2, 3, 0, 0, 0, 1, 1, 2, 0, 0, 1, 0],
       [0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 1, 1, 1, 1, 1, 2, 2, 2, 3],
       [0, 1, 2, 3, 0, 1, 2, 0, 1, 0, 0, 1, 2, 0, 1, 0, 0, 1, 0, 0]])

into this:

                                   a
array([[0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 1, 1, 1, 1, 1, 2, 2, 2, 3],
        0, 0, 0, 0, 1, 1, 1, 2, 2, 3, 0, 0, 0, 1, 1, 2, 0, 0, 1, 0],
        0, 1, 2, 3, 0, 1, 2, 0, 1, 0, 0, 1, 2, 0, 1, 0, 0, 1, 0, 0]])

Note: the columns are kept intact - see column a. They are sorted first by the first element in the column, then the second, then the third.

Thanks

도움이 되었습니까?

해결책

Maybe you could use lexsort?

>>> arr[:,np.lexsort(arr[::-1])]
array([[0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 1, 1, 1, 1, 1, 2, 2, 2, 3],
       [0, 0, 0, 0, 1, 1, 1, 2, 2, 3, 0, 0, 0, 1, 1, 2, 0, 0, 1, 0],
       [0, 1, 2, 3, 0, 1, 2, 0, 1, 0, 0, 1, 2, 0, 1, 0, 0, 1, 0, 0]])

다른 팁

Make each line a tuple and use it as a sort criterion:

a = np.array([[0, 0, 0, 0, 1, 1, 1, 2, 2, 3, 0, 0, 0, 1, 1, 2, 0, 0, 1, 0],
       [0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 1, 1, 1, 1, 1, 2, 2, 2, 3],
       [0, 1, 2, 3, 0, 1, 2, 0, 1, 0, 0, 1, 2, 0, 1, 0, 0, 1, 0, 0]])

np.array(sorted(a, key=tuple))

Out:

array([[0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 1, 1, 1, 1, 1, 2, 2, 2, 3],
       [0, 0, 0, 0, 1, 1, 1, 2, 2, 3, 0, 0, 0, 1, 1, 2, 0, 0, 1, 0],
       [0, 1, 2, 3, 0, 1, 2, 0, 1, 0, 0, 1, 2, 0, 1, 0, 0, 1, 0, 0]])
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