IIR filter design

-->ystr=[ 'type (lp, hp, bp, sb) ';
-->    'order (integer)';
-->    'design (butt, cheb1, cheb2 , ellip)' ;
-->    'cut-off frequencies (2-vector in [0, 0.5])';
-->    'error values  0 delta(1),delta(2) 1 '];
-->w=x_mdialog('Choose filter type and parameters',...
-->    ystr,['bp';'3';'ellip';'0.15 0.25';'0.08 0.035'])
 w  =
!bp          !
!            !
!3           !
!            !
!ellip       !
!            !
!0.15 0.25   !
!            !
!0.08 0.035  !
-->if w<>[] then
-->  hz=iir(evstr(w(2)),w(1),w(3),evstr(w(4)),evstr(w(5)));
-->  [hzm,fr]=frmag(hz,256);
-->  xselect();
-->  plot2d(fr',hzm')
-->  xtitle('Discrete IIR filter '+'( '+ w(3)+' ) ',' ',' ');
-->end