Matlab returns inf for the eigenvalues for an overdetermined linear system with the eig function, but the eigenvalues should not return infinit.
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I am currently solving linear systems with the eig() function and the eigenvalues that it returns are infinit. How can I solve this? (The eigenvalues should not be infinit)
My actual matrix is rather large so I use a example here for simplicity. We have the following linear differential system:
dx1/dt= 3x1
0 = x1 - x2
The solutions are of the form x= [c1 c2] e^Lt
To solve this differential equation I have the following matrices.
>> A = [1 0;0 0];
>> B = [3 0;1 -1];
With which I use the eig function to solve this problem for L. The eigenvalues that it should return are 3 and 3. But however, it returns:
>> A = [1 0;0 0];
>> B = [3 0;1 -1];
>> E = eig(B,A)
E =
-Inf
3
How can I solve this? If anything is unclear, please let me know.
4 个评论
Ryan G
2013-5-14
A is singular. According to the doc, it is trying to solve the problem
A^-1*B = gamma
So if you try to do this in MATLAB it will give you an inf matrix for A inverse due to the singularity. The documentation states that the algorithm will use the QZ method when A is singular. I'm personally not familiar with it.
Dennis
2013-5-16
Ryan G
2013-5-16
What method are you using to determine there are two equivalent eigenvalues? The QZ function will give the same answer because that is how eig processes the singular matrix.
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