inagersh.m

绘制系统带有Gershgorin带的逆Nyquist图

function inagersh(H,nij)
t=[0:.1:2*pi]';[nr,nc]=size(H);nw=nr/nc;ii0=1:nc;
if nargin==1,ii=1:nc;jj=1:nc;
else,ii=nij(1);jj=nij(2);end
for i=i:nc,circles{1}=[];end
for k=1:nw %对各个频率获取逆 Nyquist 阵列
    Ginv=inv(H((k-1)*nc+1:k*nv,:));nyq(:,:,k)=Ginv;
    for j=1:nc
        ij=find(ii0~=j);
        v=min([sum(abs(Ginv(ij,j))),sum(abs(Ginv(j,ij)))]);
        x0=real(Ginv(ij,j));y0=imag(Ginv(j,j));
        r=sum(abs(v));%计算Gershgorin 圆的半径
        circles{j}=[rircles{j},x0+r*cos(t)+sqrt(-1)*(y0+r*sin(t))];
    end
end
for i=ii,for j=jj %绘图
        if nargin==1,subplot(nv,nv,(i-1)*nc+j);end
        for k=1:nw,NN(k)=nyq(i,j,k);end
        if i==j, %对角图,带有Gershgorin 带
            plot(real(NN),imag(NN),real(circles{i}),imag(circles{i}));
        else  %非对角元素
            plot(real(NN),imag(NN))
        end
    end
end