plotting eigen vectors (nomal modes ) of a 9x9 matrix

Question

gild kone 2019-7-18

0
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此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/472387-plotting-eigen-vectors-nomal-modes-of-a-9x9-matrix

回答： johnson wul 2019-8-15

I have a matlab code for solving eigenvalues and eigenvectors problems but the ways is that i can normally plot differents eigenvalues of my matrix which depend on the varible x=-1:1. My problem is that I don't know how to plot in 3D the corresponding eigenvectors ( ie xlabel: x=-1:1, ylabel: y=-1:1 and Zlabel: z=eigenvectors )

This the correpondint code :

close all;clear all; U =0.9; f= 39; nx=f;T=1; 
x=-3.086476993000499:3.096476993000599; y=x;
A=zeros(nx,nx);   B=zeros(nx,nx); mat=zeros(nx,nx);  
for kappa=1:numel(x)  % nu=1:f-1            
 Rep = T.*(2.0.*cos(x(kappa)/2.0).*cos(x(kappa).*f/2.0)); Imp = 0.0; 
 Req = T.*(1.0 + cos(x(kappa)));  Imq = T.*(sin(x(kappa)));
 A(1,1)=U ; A(1,2)=sqrt(2.0)*Req;  A(2,1)=sqrt(2.0)*Req; 
B(1,2)=sqrt(2.0)*Imq;   B(2,1)=-sqrt(2.0)*Imq;
 for i=2:nx-1
A(i,i+1)=Req; A(i+1,i)=Req ;B(i,i+1)=Imq; B(i+1,i)=-Imq;
 end
A(nx,nx)=Rep ; B(nx,nx)=Imp;
 for i=nx:-1:1
for j=nx:-1:1
    
mat(i,j)=A(i,j);
mat(i,j+nx)=B(i,j);
mat(i+nx,j)=-B(i,j);
mat(i+nx,j+nx)=A(i,j);
end
 end
[v,d0] = eig(mat);   % eigenvectors and eigenvalues
 %vv=v(:,kappa) ; v0=vv/norm(vv); C0=v0.*v0        % give us \c0\^2
        dd=d(:,kappa); d0=dd/norm(dd); z=d0*d0' ; surf(z); 
   %d0(kappa,:)=eig(mat); for eigenvalue only 
end
% plot(d0,'r-');