filtic zf = filtic (b, a, y) zf = filtic (b, a, y, x) b: vector of real or complex numbers a: vector of real or complex numbers y: vector of real or complex numbers x: vector of real or complex numbers This function finds the initial conditions for the delays in the transposed direct-form II filter implementation. The vectors b and a represent the numerator and denominator coefficients of the filter's transfer function.