trfmod poles and zeros display

## Syntax

    [hm]=trfmod(h [,job])

## Description

To visualize the pole-zero structure of a SISO transfer function `h` .

job='p'

  visualization of polynomials (default)

job='f'

  visualization of natural frequencies and damping

Interactive simplification of `h`. `trfmod` opens a dialog window.

## Examples

    // with a transfer function
    s=poly(0,'s');
    gs=syslin('c',1/(s+1));
    trfmod(gs)

    // with a state-space matrix
    A=diag([1,2,3]);
    B=[1;1;1];
    C=[2,2,2];
    sys=syslin('c',A,B,C);
    trfmod(sys)

## See also

- poly
- simp