Question

I’m trying to understand how to transform a filter, in this case a Notch(stopband) filter, to Python but I don’t know how.

x(n)=-2*x(n)/(-0.9*x(n) -0.9*x(n-1))

Can anyone help me please?

Thanks in advance.

Answer 1

If you’re using numpy arrays, this should work:

x[1:]=-2*x[1:]/(-0.9*x[1:]-0.9*x[:-1])

this changes your array in place, but you could just as easily assign it to a new array.

y=-2*x[1:]/(-0.9*x[1:]-0.9*x[:-1])

Note that your algorithm isn’t really well defined for the 0th element, so my translation leaves x[0] unchanged.

EDIT

To change an iterable to a numpy array:

import numpy as np
x=np.array(iterable)  #pretty easy :) although there could be more efficient ways depending on where "iterable" comes from.