windstable=figure('color',[1,0.9,0.9],'position',[0.25*winw,0.25*winh,0.5*winw,0.5*winh],...
       'name','離散系統穩定性','numbertitle','off','menubar','none',...
        'resize','off');
color=[0.2,0.6,0.1];
uicontrol('style','frame','position',[0,0,1,1],'units','normalized','backgroundcolor',color);
color=[0;0.8;1];
uicontrol('style','frame','position',[0.075,0.2,.85,.7],...
   'units','normalized','backgroundcolor',color);
rr1=size(dfbnum);
rr2=size(dfbden);
finderr=0;
%判斷是否為比例環節
if ((rr1(1,2)==1)&(rr2(1,2)==1)),
   finderr=1;
   pos=[0.1,0.65,0.8,0.1];
   showtext(pos,color,'系統為比例環節');break
end
n=length(dak);dek=0;     
for i=1:n
   dek(i,i)=1;
end
n=length(da);de=0;
for i=1:n
   de(i,i)=1;
end  

dsysb=dss(da,db,dc,dd,de,dhT); 
dsysk=dss(dak,dbk,dck,ddk,dek,dhT);    
ddpb=pole(dsysb);
pos=[0.1,0.47,0.8,0.1];
ii=find(abs(ddpb)>=1);n1=length(ii);
if (n1>0)
   pos=[0.1,0.65,0.8,0.1];
   showtext(pos,color,'系統不穩定，');
   pos=[0.1,0.47,0.8,0.1];
   showtext(pos,color,'極點分布判據：極點并非都分布在單位圓內：系統不穩定');
else
   pos=[0.1,0.65,0.8,0.1];
   pos(2)=0.65;showtext(pos,color,'系統穩定');
   pos=[0.1,0.65,0.8,0.1];
   pos(2)=0.47;showtext(pos,color,'極點分布判據：極點都分布單位圓內：系統穩定');
end
pos(2)=0.28;showtext(pos,color,'參見系統零極點分布及根軌跡圖');
uicontrol(windstable,'style','push','string','Ok',...
       'position',[0.39,0.06,0.22,0.09],'units','normalized',...
      'callback','dmyrootb,close(windstable)');