def ss2zpk(A, B, C, D, input=0):
 return tf2zpk(*ss2tf(A, B, C, D, input=input))

def ss2zpk ( A , B , C , D , input = 0 ) : return tf2zpk ( * ss2tf ( A , B , C , D , input = input ) )
state-space representation to zero-pole-gain representation .