butter - BUTTERWORTH FILTER DESIGN IN Z-DOMAIN
This function calculates the filter coefficients for a butterworth filter in the z-domain, so that the output value of the filter is given by:
a(1)*y(n) = b(1)*x(n) + b(2)*x(n-1) + ... + b(nb+1)*x(n-nb) - a(2)*y(n-1) - ... - a(na+1)*y(n-na)
This function emulates the MatLab Butter function from the signal toolbox. For the realization the SciLab-functions "iir", "coeff", "denom" and "numer" are used. If the filtertype is 'bp' or 'sb', then you need a vector for the argument filterfreq.
[B,A]=butter(8,'lp'); x=rand(1,300,'normal'); y=mtlb_filter(B,A,x); t=0:1:299; plot2d(t,x,style=3); plot2d(t,y,style=2); // end of example butter