w = logspace(-1,3,50); wsel = logspace(-1,3,10);
pa = nd2sys(1,[1 1]);
pb = nd2sys(1,[.1 1]);
pstack = vpck([pa;scale(pa,10);scale(pb,10);pb;pa],[1;2;3;4;5]);
gvar= veval('frsp',pstack,wsel);
gnic= veval('vunpck',gvar);
gbode = veval('vunpck',swapiv(gvar,[2 1]));
vplot('nyq',gnic);pause
vplot('nic',gnic);pause
vplot('bode',gbode);

