python - 在二维数组中创建规则网格的 Numpy 例程

Question

我正在尝试编写一个函数，在二维数组中创建一个 5 x 5 像素的规则网格。我希望 numpy.arange 和 numpy.repeat 的一些组合可以做到这一点，但到目前为止我还没有任何运气，因为 numpy.repeat 只会沿着同一行重复。

这是一个例子:

假设我想在形状为 (20, 15) 的二维数组中放置一个 5x5 的网格。它应该看起来像:

array([[ 0, 0, 0, 0, 0, 1, 1, 1, 1, 1, 2, 2, 2, 2, 2],
       [ 0, 0, 0, 0, 0, 1, 1, 1, 1, 1, 2, 2, 2, 2, 2],
       [ 0, 0, 0, 0, 0, 1, 1, 1, 1, 1, 2, 2, 2, 2, 2],
       [ 0, 0, 0, 0, 0, 1, 1, 1, 1, 1, 2, 2, 2, 2, 2],
       [ 0, 0, 0, 0, 0, 1, 1, 1, 1, 1, 2, 2, 2, 2, 2],
       [ 3, 3, 3, 3, 3, 4, 4, 4, 4, 4, 5, 5, 5, 5, 5],
       [ 3, 3, 3, 3, 3, 4, 4, 4, 4, 4, 5, 5, 5, 5, 5],
       [ 3, 3, 3, 3, 3, 4, 4, 4, 4, 4, 5, 5, 5, 5, 5],
       [ 3, 3, 3, 3, 3, 4, 4, 4, 4, 4, 5, 5, 5, 5, 5],
       [ 3, 3, 3, 3, 3, 4, 4, 4, 4, 4, 5, 5, 5, 5, 5],
       [ 6, 6, 6, 6, 6, 7, 7, 7, 7, 7, 8, 8, 8, 8, 8],
       [ 6, 6, 6, 6, 6, 7, 7, 7, 7, 7, 8, 8, 8, 8, 8],
       [ 6, 6, 6, 6, 6, 7, 7, 7, 7, 7, 8, 8, 8, 8, 8],
       [ 6, 6, 6, 6, 6, 7, 7, 7, 7, 7, 8, 8, 8, 8, 8],
       [ 6, 6, 6, 6, 6, 7, 7, 7, 7, 7, 8, 8, 8, 8, 8],
       [ 9, 9, 9, 9, 9,10,10,10,10,10,11,11,11,11,11],
       [ 9, 9, 9, 9, 9,10,10,10,10,10,11,11,11,11,11],
       [ 9, 9, 9, 9, 9,10,10,10,10,10,11,11,11,11,11],
       [ 9, 9, 9, 9, 9,10,10,10,10,10,11,11,11,11,11],
       [ 9, 9, 9, 9, 9,10,10,10,10,10,11,11,11,11,11]])

我知道我可以简单地使用循环和切片来完成此操作，但我可能会将其应用于非常大的数组，我担心这样做的性能会太慢或不切实际。

谁能推荐一种方法来完成这个？

提前致谢。

更新:

提供的所有答案似乎都很有效。谁能告诉我哪个对大型阵列最有效？我所说的大数组是指它可以是 100000 x 100000 或更多，15 x 15 网格单元格大小。

Answer 1

广播就是这里的答案:

m, n, d = 20, 15, 5
arr = np.empty((m, n), dtype=np.int)
arr_view = arr.reshape(m // d, d, n // d, d)
vals = np.arange(m // d * n // d).reshape(m // d, 1, n // d, 1)
arr_view[:] = vals

>>> arr
array([[ 0,  0,  0,  0,  0,  1,  1,  1,  1,  1,  2,  2,  2,  2,  2],
       [ 0,  0,  0,  0,  0,  1,  1,  1,  1,  1,  2,  2,  2,  2,  2],
       [ 0,  0,  0,  0,  0,  1,  1,  1,  1,  1,  2,  2,  2,  2,  2],
       [ 0,  0,  0,  0,  0,  1,  1,  1,  1,  1,  2,  2,  2,  2,  2],
       [ 0,  0,  0,  0,  0,  1,  1,  1,  1,  1,  2,  2,  2,  2,  2],
       [ 3,  3,  3,  3,  3,  4,  4,  4,  4,  4,  5,  5,  5,  5,  5],
       [ 3,  3,  3,  3,  3,  4,  4,  4,  4,  4,  5,  5,  5,  5,  5],
       [ 3,  3,  3,  3,  3,  4,  4,  4,  4,  4,  5,  5,  5,  5,  5],
       [ 3,  3,  3,  3,  3,  4,  4,  4,  4,  4,  5,  5,  5,  5,  5],
       [ 3,  3,  3,  3,  3,  4,  4,  4,  4,  4,  5,  5,  5,  5,  5],
       [ 6,  6,  6,  6,  6,  7,  7,  7,  7,  7,  8,  8,  8,  8,  8],
       [ 6,  6,  6,  6,  6,  7,  7,  7,  7,  7,  8,  8,  8,  8,  8],
       [ 6,  6,  6,  6,  6,  7,  7,  7,  7,  7,  8,  8,  8,  8,  8],
       [ 6,  6,  6,  6,  6,  7,  7,  7,  7,  7,  8,  8,  8,  8,  8],
       [ 6,  6,  6,  6,  6,  7,  7,  7,  7,  7,  8,  8,  8,  8,  8],
       [ 9,  9,  9,  9,  9, 10, 10, 10, 10, 10, 11, 11, 11, 11, 11],
       [ 9,  9,  9,  9,  9, 10, 10, 10, 10, 10, 11, 11, 11, 11, 11],
       [ 9,  9,  9,  9,  9, 10, 10, 10, 10, 10, 11, 11, 11, 11, 11],
       [ 9,  9,  9,  9,  9, 10, 10, 10, 10, 10, 11, 11, 11, 11, 11],
       [ 9,  9,  9,  9,  9, 10, 10, 10, 10, 10, 11, 11, 11, 11, 11]])