des2ss

Scilab Function
Last update : 25/04/2007

des2ss - descriptor to state-space

### Calling Sequence

  `[Sl]=des2ss(A,B,C,D,E [,tol])`
  `[Sl]=des2ss(Des)`

### Parameters

- `A,B,C,D,E` : real matrices of appropriate dimensions
- `Des` : list
- `Sl` : `syslin` list
- `tol` : real parameter (threshold) (default value `100*%eps` ).

### Description

Descriptor to state-space transform.

`Sl=des2ss(A,B,C,D,E)` returns a linear system `Sl` equivalent to the descriptor system `(E,A,B,C,D)` .

For index one `(E,A)` pencil, explicit formula is used and for higher index pencils `rowshuff` is used.

`Sl=des2ss(Des)` with `Des=list('des',A,B,C,D,E)` returns a linear system `Sl` in state-space form with possibly a polynomial `D` matrix.

A generalized Leverrier algorithm is used.

### Examples

    s=poly(0,'s');G=[1/(s-1),s;1,2/s^3];
    S1=tf2des(G);S2=tf2des(G,"withD");
    W1=des2ss(S1);W2=des2ss(S2);
    clean(ss2tf(W1))
    clean(ss2tf(W2))

### See Also

`des2tf` , `glever` , `rowshuff` ,