Scilab Function

iirgroup - group delay Lp IIR filter optimization

### Sequence d'appel

  `[lt,grad]=iirgroup(p,r,theta,omega,wt,td)`
  `[cout,grad,ind]=iirlp(x,ind,p,[flag],lambda,omega,ad,wa,td,wt)`

### Parametres

- `r` : vector of the module of the poles and the zeros of the filters
- `theta` : vector of the argument of the poles and the zeros of the filters
- `omega` : frequencies where the filter specifications are given
- `wt` : weighting function for and the group delay
- `td` : desired group delay
- `lt, grad` : criterium and gradient values

### Description

optimization of IIR filters for the Lp criterium for the the group delay. (Rabiner & Gold pp270-273).