Wang Chengbin wrote:
> I got the following error:
>
> a = read.csv("mat.csv")
> b = as.matrix(a)
> tb = t(b)
> bb = tb %*% b
> dim(bb)
> ibb = solve(bb)
> bb %*% ibb
>
>
>> ibb = solve(bb)
>>
> Error in solve.default(bb) :
> system is computationally singular: reciprocal condition number =
> 1.77573e-19
>
> Are there any ways to find more information about why it is singular?
>
> Thanks.
>
Yes. Since the matrix is positive semidefinite by construction, I'd
probably go for chol(bb, pivot=TRUE), then the first "rank" elements of
"pivot" gives you a maximal subset of linearly independent columns, and
you can proceed by something like lm(b[,-subset]~b[,subset]) to see what
the linear dependencies are.
(Other approaches could be eigen() and svd().)
--
O__ ---- Peter Dalgaard Øster Farimagsgade 5, Entr.B
c/ /'_ --- Dept. of Biostatistics PO Box 2099, 1014 Cph. K
(*) \(*) -- University of Copenhagen Denmark Ph: (+45) 35327918
~~~~~~~~~~ - ([EMAIL PROTECTED]) FAX: (+45) 35327907
______________________________________________
R-help@r-project.org mailing list
https://stat.ethz.ch/mailman/listinfo/r-help
PLEASE do read the posting guide http://www.R-project.org/posting-guide.html
and provide commented, minimal, self-contained, reproducible code.
