impz It gives Impulse response of digital filter x_r = impz(b) x_r = impz(b, a) x_r = impz(b, a, n) x_r = impz(b, a, n, fs) [x_r, t_r] = impz(b, a, n, fs) x_r: impz chooses the number of samples and returns the response in the column vector, x_r. t_r: impz returns the sample times in the column vector, t_r b: numerator coefficients of the filter a: denominator coefficients of the filter n: samples of the impulse response t(by default ,n = length(t) and is computed automatically. fs: sampling frequency [x_r,t_r] = impz(b,a) returns the impulse response of the filter with numerator coefficients, b, and denominator coefficients, a. impz chooses the number of samples and returns the response in the column vector, x_r, and the sample times in the column vector, t_r. t_r = [0:n-1]' and n = length(t) is computed automatically.