function [a, b, c, d] = zp2ss (z, p, k)
    //Converts zeros / poles to state space.
    //Calling Sequence
    //[a, b, c, d] = zp2ss (z, p, k)
    //[a, b, c] = zp2ss (z, p, k)
    //[a, b] = zp2ss (z, p, k)
    //a = zp2ss (z, p, k)
    //Parameters
    //z: Zeros
    //p: Poles
    //k: Leading coefficient
    //a: State space parameter
    //a: State space parameter
    //b: State space parameter
    //c: State space parameter
    //d: State space parameter
    //Description
    //This is an Octave function.
    //It converts zeros / poles to state space.
    //Examples
    //z = [1 2 3]
    // p = [4 5 6]
    //k = 5
    //[a, b, c, d] = zp2ss (z, p, k)
    //a =
    //
    //   -0.00000    0.00000   -1.20000
    //  -10.00000    0.00000   -7.40000
    //    0.00000   10.00000   15.00000
    //
    //b =
    //
    //   -5.7000
    //  -31.5000
    //   45.0000
    //
    //c =
    //
    //   0.00000   0.00000   1.00000
    //
    //d =  5

    funcprot(0);
    lhs = argn(1)
    rhs = argn(2)
    if (rhs < 3 | rhs > 3)
        error("zp2ss: Wrong number of input arguments.")
    end
    [num den] = zp2tf(z,p,k);
    h = poly(num, "s", "c")/poly(den, "s", "c");
    sys = tf2ss(num, den)
    [a b c d] = abcd(sys)

endfunction