[R-sig-Geo] Eigenvalues for eigenvectors extracted using ME() of spdep

[Roger Bivand]

On Wed, 28 Jan 2009, Xingli Giam wrote:

> Hi everyone,
>
> I hope someone can point me to the right direction in printing the eigenvalues
> of selected eigenvectors using ME() of spdep. I've communicated with Dr. Pedro
> Peres-Neto and he has been really helpful in answering some of my questions
> about SEVM. He warned that some combinations of threshold values and weighting
> schemes may generate negative eigenvalues that may not be desirable. That is
> why I'm asking this question.

The eigenvalues are not (at present) available. If you need them now, do:

debug(ME)

run your ME(...) command, and step through until you see the line:

 	eV <- eigen(Cent %*% Wmat %*% Cent, EISPACK=TRUE)$vectors

Enter:
my_eigenvalues <<- eigen(Cent %*% Wmat %*% Cent, EISPACK=TRUE)$values

then use "c" to "continue" through the debugging. This should assign the 
eigenvalues of the same matrix to my_eigenvalues in your global 
environment. Remember to say undebug(ME) afterwards.

If you (or others) would find it useful, I can add an argument to return 
the eigenvalues as an attribute of the output object when requested.

Hope this helps,

Roger

>
> Thanks in advance!
>
> Best,
> Xingli
>
>
>

-- 
Roger Bivand
Economic Geography Section, Department of Economics, Norwegian School of
Economics and Business Administration, Helleveien 30, N-5045 Bergen,
Norway. voice: +47 55 95 93 55; fax +47 55 95 95 43
e-mail: Roger.Bivand at nhh.no