arma2p extract polynomial matrices from ar representation

## Syntax

    [A, B, D] = arma2p(ar)

## Arguments

A,B,D

  three polynomial matrices

ar

  Scilab 'ar' tlist for arma storage (see `armac`).

## Description

this function extract polynomial matrices `(A,B,D)` from an armax description.

## Examples

    a=[1,-2.851,2.717,-0.865].*.eye(2,2)
    b=[0,1,1,1].*.[1;1];
    d=[1,0.7,0.2].*.eye(2,2);
    sig=eye(2,2);
    ar=armac(a,b,d,2,1,sig)
    // extract polynomial matrices from ar representation
    [A,B,D]=arma2p(ar);

## See also

- arma
- armax
- armax1
- arsimul
- armac