I am trying to implement 1D-convolution for signals.
It should have the same output as:
ary1 = np.array([1, 1, 2, 2, 1])
ary2 = np.array([1, 1, 1, 3])
conv_ary = np.convolve(ary2, ary1, 'full')
>>>> [1 2 4 8 8 9 7 3]
I came up with this approach:
def convolve_1d(signal, kernel):
n_sig = signal.size
n_ker = kernel.size
n_conv = n_sig - n_ker + 1
# by a factor of 3.
rev_kernel = kernel[::-1].copy()
result = np.zeros(n_conv, dtype=np.double)
for i in range(n_conv):
result[i] = np.dot(signal[i: i + n_ker], rev_kernel)
return result
But my result is [8,8]
I might have to zero pad my array instead and change its indexing.
Is there a smoother way to achieve the desired outcome?
Here is a possible solution:
def convolve_1d(signal, kernel):
kernel = kernel[::-1]
return [
np.dot(
signal[max(0,i):min(i+len(kernel),len(signal))],
kernel[max(-i,0):len(signal)-i*(len(signal)-len(kernel)<i)],
)
for i in range(1-len(kernel),len(signal))
]
Here is an example:
>>> convolve_1d([1, 1, 2, 2, 1], [1, 1, 1, 3])
[1, 2, 4, 8, 8, 9, 7, 3]