//exec('group6_8.code')
//save and change dess
   xinit('group6.ps');

//create filter using ffir

   [h w]=wfir('lp',7,[.2,0],'hm',[0.01,-1]);
   [tg,fr]=group(100,h);
   plot2d(fr',tg',1,'011',' ',[0,2,0.5,4.])
   xend()

//demonstrate rational polynomial
   xinit('group7.ps');
   z=poly(0,'z');
   h=z/(z-.5);
   [tg,fr]=group(100,h);
   plot(fr,tg)
   xend()

//demonstrate cascade realization
   xinit('group8.ps');
   h=[1 1.5 -1 1;2 -2.5 -1.7 0;3 3.5 2 5];
   h=h';
   h=casc(h,'z');
   [tg,fr]=group(100,h);
   plot(fr,tg)
   xend()