butter This function generates a Butterworth filter. [a, b] = butter (n, w) [a, b] = butter (n, w, "high") [a, b] = butter (n, [wl, wh]) [b, a] = butter (n, [wl, wh], "stop") [a, b, c] = butter (…) [a, b, c, d] = butter (…) […] = butter (…, "s") n: positive integer value w: positive real value, w in the range [0,1] This is an Octave function. This function generates a Butterworth filter. Default is a discrete space (Z) filter. The third parameter takes in low or high, default value is low. The cutoff is pi*Wc radians. [b,a] = butter(n, [Wl, Wh]) indicates a band pass filter with edges pi*Wl and pi*Wh radians. [b,a] = butter(n, [Wl, Wh], ’stop’) indicates a band reject filter with edges pi*Wl and pi*Wh radians. [z,p,g] = butter(...) returns filter as zero-pole-gain rather than coefficients of the numerator and denominator polynomials. [...] = butter(...,’s’) returns a Laplace space filter, w can be larger than 1. [a,b,c,d] = butter(...) returns state-space matrices.