MATLAB: How to plot a graph for only one eigen value against a variable? I’m only getting one M!

basicblankeigenvaluegraphplot

I am trying to plot a graph for k:[0,1] against the larger eigenvalue from the corresponding matrix. i.e for each value of k I am only interested in the larger of the two eigenvalues from the 2×2 matrix M.
This is a very basic code, I know, but having played around with it for a few days now I could really use some help!
    % code
A=3.3;
B=0.45;
a=B;
b=((A+sqrt(A^2-4*B^2))/(2*B))^2;
c=-2*B;
d=-1-b;
D=500;
for k=0.0:0.01:1.0
    M=[a-k^2 b; c d-D*k^2];
    lam=eig(M);
end
plot(k,lam)
  end

Best Answer

I have slightly modified your code. I hope this will help!
A=3.3;
B=0.45;
a=B;
b=((A+sqrt(A^2-4*B^2))/(2*B))^2;
c=-2*B;
d=-1-b;
D=500;
k = (0:0.01:1);
lam = zeros(2,length(k));
for kk = 1:length(k)
  M=[a-k(kk)^2 b; c d-D*k(kk)^2];
  lam(:,kk)=eig(M);
end
plot(k,lam)
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