numpy.convolve 如何完成它的工作？

Question

thanks to this link enter link description here , I've got a sense about numpy.correlate function.

[3 4]
[1 1 5 5]
= 3 * 1 + 4 * 1 = 7
  [3 4]
[1 1 5 5]
= 3 * 1 + 4 * 5 = 23
    [3 4]
[1 1 5 5]
= 3 * 5 + 4 * 5 = 35

my question is, how dose numpy.convolve do its job, which gives this result?

>>>np.convolve(W,X,'valid')
array([ 7, 19, 35])

how does numpy get the value 19 in the middle?

thanks in advance!

Answer 1

Per your link:

The convolution of two signals is defined as the integral of the first signal, reversed , sweeping over ("convolved onto") the second signal and multiplied (with the scalar product) at each position of overlapping vectors.

You missed the bolded part. So what happens is actually this:

np.convolve([3, 4], [1, 1, 5, 5], 'valid')

4 * 1 + 3 * 1 = 7
4 * 1 + 3 * 5 = 19
4 * 5 + 3 * 5 = 35