相关疑难解决方法(0)

我想以这种形式计算Python中数组的平均值:

Matrice = [1, 2, None]

我只是想None通过numpy.mean计算忽略我的价值,但我无法弄清楚如何去做.

问:如何加快速度？

下面是我对Matlab的im2col '滑动'的实现,以及返回每个第n列的附加功能.该函数采用图像(或任意2个暗淡的数组)并从左到右,从上到下滑动,拾取给定大小的每个重叠子图像,并返回其列为子图像的数组.

import numpy as np

def im2col_sliding(image, block_size, skip=1):

    rows, cols = image.shape
    horz_blocks = cols - block_size[1] + 1
    vert_blocks = rows - block_size[0] + 1

    output_vectors = np.zeros((block_size[0] * block_size[1], horz_blocks * vert_blocks))
    itr = 0
    for v_b in xrange(vert_blocks):
        for h_b in xrange(horz_blocks):
            output_vectors[:, itr] = image[v_b: v_b + block_size[0], h_b: h_b + block_size[1]].ravel()
            itr += 1

    return output_vectors[:, ::skip]

例:

a = np.arange(16).reshape(4, 4)
print a
print im2col_sliding(a, (2, 2))  # return every …