nyquist1.m

xnsy算法的matlab实现

%nyquist
ngwin=figure('Position',[120 49 513 491],'Name','描述函数法','NumberTitle','off',...
      'MenuBar','none');

axes('position',[0 0 1 1]);
axis off;
dd=text(0.1,0.18,'实轴范围:');
set(dd,'fontsize',15,'color',[1 1 1],'fontname','宋体');
dd=text(0.1,0.08,'虚轴范围:');
set(dd,'fontsize',15,'color',[1 1 1],'fontname','宋体');

%设置绘图区域
axes('Position',[.15 .33 .8 .56]);
%绘制乃氏图
nyquist(N,D);
grid;
set(gcf,'name','开环Nyquist图');

axis0=axis;
xaxis=[axis0(1),axis0(2)];  %横坐标轴范围
yaxis=[axis0(3),axis0(4)];  %纵坐标轴范围

% 改变坐标轴范围时，判断输入是否正确，如正确，设置坐标轴范围；
%  否则，弹出错误信息，恢复原坐标轴范围
axis_com=['xaxis=eval(get(x_edit,''string''));yaxis=eval(get(y_edit,''string''));',...
          'if (xaxis(1)<xaxis(2))&(yaxis(1)<yaxis(2))',...
          '   axis([xaxis yaxis]);',...
          'else  ',...  
          '   errordlg(''坐标轴输入错误!'',''错误信息'',''on'');',...
          '   axis0=axis;',...
          '   xaxis=[axis0(1),axis0(2)];',... 
          '   yaxis=[axis0(3),axis0(4)];',... 
          '   set(x_edit,''string'',[''['',num2str(xaxis(1)),'' '',num2str(xaxis(2)),'']'']);',...
          '   set(y_edit,''string'',[''['',num2str(yaxis(1)),'' '',num2str(yaxis(2)),'']'']);',...          
          'end;'];

% 横轴范围输入框
x_edit=uicontrol(ngwin,'style','edit','units','normalized',...
       'position',[0.3,0.15,0.3,0.05],'string',['[',num2str(xaxis(1)),' ',num2str(xaxis(2)),']'],'back',[1 1 1],...
       'call',axis_com);
% 纵轴范围输入框
y_edit=uicontrol(ngwin,'style','edit','units','normalized',...
       'position',[0.3,0.05,0.3,0.05],'string',['[',num2str(yaxis(1)),' ',num2str(yaxis(2)),']'],'back',[1 1 1],...
       'call',axis_com);

% 关闭按钮
uicontrol('style','push','units','normal','pos',[0.7 0.05 0.13 0.05],'string','&Close',...
         'call','close')