从Numpy 3D阵列保留切片的尺寸 [英] Preserving the dimensions of a slice from a Numpy 3d array

问题描述

我有一个形状为a.shape = (10, 10, 10)

切片时，尺寸会自动squeezed，即

When slicing, the dimensions are squeezed automatically i.e.

a[:,:,5].shape = (10, 10)

我想保留维度的数量，但还要确保压缩的维度是显示1的维度.

I'd like to preserve the number of dimensions but also ensure that the dimension that was squeezed is the one that shows 1 i.e.

a[:,:,5].shape = (10, 10, 1)

我曾考虑过重新铸造数组并传递ndmin，但这只是将额外的维添加到形状元组的开头，而不管切片来自数组a的何处.

I have thought of re-casting the array and passing ndmin but that just adds the extra dimensions to the start of the shape tuple regardless of where the slice came from in the array a.

推荐答案

a[:,:,[5]].shape
# (10,10,1)

---

a[:,:,5]是基本切片.

a[:,:,[5]]是整数的示例数组索引-结合基本切片.使用整数数组索引时，结果形状始终为与(广播的)索引数组形状相同" .由于[5](作为数组)的形状为(1,)， a[:,:,[5]]最终形状为(10,10,1).

a[:,:,[5]] is an example of integer array indexing -- combined with basic slicing. When using integer array indexing the resultant shape is always "identical to the (broadcast) indexing array shapes". Since [5] (as an array) has shape (1,), a[:,:,[5]] ends up having shape (10,10,1).

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