zeropen

zeropen — zero pencil

Calling sequence

[Z,U]=zeropen(Sl)

`Sl`	: a linear system (`syslin` list in state-space form `[A,B,C,D]`)
`Z`	: matrix pencil `Z=s*E-A`
`U`	: square orthogonal matrix

Z = sE - F is the zero pencil of the linear system Sl with matrices [A,B,C,D]. Utility function.

With U row compression of [B;D] i.e, U*[B;D]=[0;*]; one has:



U*[-sI+A |B;   [ Z |0;      
      C  |D] = [ * |*]

The zeros of Z are the zeros of Sl.