Thread: Finding eigenvalues for any size of matrices?

I have a problem, I need to find eigenvalues of two matrices which are k and m. I am stuck please help me . Here is my problem

1. I need to find eigenvalues for any size k and m (may be 1000-by-1000 or larger) by using matlab
2. some values of k are very big as like 1e30

Thanks for your help...

Hi.

Originally Posted by woundedeagle

I have a problem, I am working on my thesis and I need to find eigenvalues of two matrices which are k and m. I am stuck please help me . Here is my problem

1. I need to find eigenvalues for any size k and m (may be 1000-by-1000 or larger) by using matlab
2. some values of k are very big as like 1e30

I don't get it, why not using this code: (A is your matrix)

eig(A)


matlab probably finds the eigenvalues. Otherwise: what exactly was your question?

Cheers,
Rapha

Edit:

As far as I know, matlab eig command can't calculate huge values such as 1e+30 exactly.

I don't know. Why don't you try out an example and test it?

So I need to calculate exact eigenvalues for very large matrices like 1000-by-1000. Do you know anything about it?

No, I do not.

Have you ever heard that eig command can't calculate big values?

No.

Originally Posted by Rapha

Hi.



I don't get it, why not using this code: (A is your matrix)

eig(A)


matlab probably finds the eigenvalues. Otherwise: what exactly was your question?

Cheers,
Rapha

As far as I know, matlab eig command can't calculate huge values such as 1e+30 exactly. So I need to calculate exact eigenvalues for very large matrices like 1000-by-1000. Do you know anything about it? Have you ever heard that eig command can't calculate big values?

thank you for your reply I need to focus on LAPACK routine I guess...

Originally Posted by woundedeagle

I have a problem, I am working on my thesis and I need to find eigenvalues of two matrices which are k and m. I am stuck please help me . Here is my problem

1. I need to find eigenvalues for any size k and m (may be 1000-by-1000 or larger) by using matlab
2. some values of k are very big as like 1e30

Thanks for your help...

Look at the help system for sparse matrix calculations. If your matruices are not sparse you will be bound by memory constaints, but 1000x1000 should be with in the limits of a modern PC.

CB