根据另一个数组中的出现替换二维数组中的元素 [英] Replace elements in 2D array based on occurrence in another array

问题描述

我需要根据元素出现在其他 replacement 数组

I need to replace elements in Numpy 2D arrays based on a condition that the element appears in some other replacement array

例如:

>>> main = np.random.randint(5, size=(3, 4))
>>> main
array([[1, 2, 4, 2],
   [3, 2, 3, 2],
   [4, 4, 2, 3]])
>>> repl = [2,3]
>>> main[main in repl] = -1

我想将 repl 中的所有值都更改为-1，所以我希望main为:

I would like to have all values in repl changed to -1, so I expect main to be:

[[1, -1, 4, -1],
[-1, -1, -1, -1],
[4, 4, -1, -1]]

但是，在尝试使 in 处于替换条件之内时，引发了 ValueError

However a ValueError is raised while trying to have in inside the condition of replacement

ValueError:具有多个元素的数组的真值不明确.使用a.any()或a.all()

ValueError: The truth value of an array with more than one element is ambiguous. Use a.any() or a.all()

推荐答案

我们可以使用 np.in1d 来创建所有此类事件的展平掩码，并在展平输入中将其设置为 -1 ，如下所示-

We can use np.in1d to create a flattened mask of all such occurrences and set those as -1 in the flattened input, like so -

main.ravel()[np.in1d(main, repl)] = -1

或者，我们可以使用 np.putmask 并因此避免 np.ravel()以避免显式展平，就像这样-

Alternatively, we can use np.putmask and thus avoid np.ravel() to avoid the explicit flattening, like so -

np.putmask(main, np.in1d(main, repl), -1)

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