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Thread Subject:
Command "eig" in matlab

Subject: Command "eig" in matlab

From: Chanh

Date: 16 Jul, 2012 02:45:50

Message: 1 of 3


When I work with eigenvalude problem, I have some questions about ut.

1) function eig base on what theory is.
2) When eig with option some eigenvalue, which have differentce (about algorithm) in solving all eigenvalue?


Thanks for helping!

Subject: Command "eig" in matlab

From: Nasser M. Abbasi

Date: 16 Jul, 2012 03:02:39

Message: 2 of 3

On 7/15/2012 9:45 PM, Chanh wrote:
>
> When I work with eigenvalude problem, I have some questions about ut.
>
> 1) function eig base on what theory is.
> 2) When eig with option some eigenvalue, which have differentce
>(about algorithm) in solving all eigenvalue?
>

Did you look at help eig? It describes the algorithms used
in general. Eventually it all ends up in lapack hands at
one point or another.

For eig, look at the netlib functions to learn more
about the implementation. For example, the one for finding eigs for
real symmetric matrix is

http://www.netlib.org/lapack/single/ssyev.f

I have a table here which tells which lapack function
is used for which case

http://12000.org/my_notes/lapack_analysis/lapack/lapack.htm

Different algorithms are used depending on the structure
of A. Again, start with help eig()

--Nasser

Subject: Command "eig" in matlab

From: Greg Heath

Date: 17 Jul, 2012 02:10:34

Message: 3 of 3

"Nasser M. Abbasi" <nma@12000.org> wrote in message <ju008f$uk0$1@speranza.aioe.org>...
> On 7/15/2012 9:45 PM, Chanh wrote:
> >
> > When I work with eigenvalude problem, I have some questions about ut.
> >
> > 1) function eig base on what theory is.
> > 2) When eig with option some eigenvalue, which have differentce
> >(about algorithm) in solving all eigenvalue?
> >
>
> Did you look at help eig? It describes the algorithms used
> in general. Eventually it all ends up in lapack hands at
> one point or another.
>
> For eig, look at the netlib functions to learn more
> about the implementation. For example, the one for finding eigs for
> real symmetric matrix is
>
> http://www.netlib.org/lapack/single/ssyev.f
>
> I have a table here which tells which lapack function
> is used for which case
>
> http://12000.org/my_notes/lapack_analysis/lapack/lapack.htm
>
> Different algorithms are used depending on the structure
> of A. Again, start with help eig()

Sometimes additional information is obtained using the command doc, e.g.,

doc eig

Hope this helps.

Greg

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