>> y(n) = k2*x(n) + k1*(1+k2)*x(n-1) + x(n-2) - k1*(1+k2)*y(n-1) - k2*y(n-2) > > Hey thanks. That answers a ton for me. I guess the last thing I had > on my mind was in regards to n. > > Since X would be a trace containing an array of samples, x would > contain the first sample. In the algorithm, there is a point where it > is asking for x[n-1] and x[n-2]. In the case that n would equal 0, the > first part (n-1) would try to pull a value from the -1 element in the > array. How would I work around that for the first few elements of the > array?
Typically the signal is zero-padded. In "help filter", the function accepts "initial conditions", which would be used instead, in special applications. Block-based filtering might be one of them, where there actually are two known values for the input prior to the x in this context.