Convert transfer function filter parameters to state-space form
[A,B,C,D] = tf2ss(b,a)
tf2ss converts the parameters of a transfer function representation of a given system to those of an equivalent state-space representation.
in controller canonical form
The input vector a contains the denominator coefficients in descending powers of s. The rows of the matrix b contain the vectors of numerator coefficients (each row corresponds to an output). In the discrete-time case, you must supply b and a to correspond to the numerator and denominator polynomials with coefficients in descending powers of z.
For discrete-time systems you must make b have the same number of columns as the length of a. You can do this by padding each numerator represented in b (and possibly the denominator represented in the vector a) with trailing zeros. You can use the function eqtflength to accomplish this if b and a are vectors of unequal lengths.
The tf2ss function is part of the standard MATLAB® language.