zeropen zero pencil

## Syntax

    [Z, U] = zeropen(Sl)

## Arguments

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

## Description

`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`.

## See also

- systmat
- kroneck