Matrix Inversion

Hello Wang

matrix bb is symmetric positive semidefinite, so
algebraically the eigenvalues are nonnegative.

I would use

bb <- crossprod(b)

to calculate bb (faster and possibly more accurate)

Look at eigen(bb,TRUE,TRUE)$values

(see ?eigen for the meaning of the arguments) to see how
many very small eigenvalues you have.  The number of zero
eigenvalues is equal to the number of linear relations
in the columns of b.


HTH


rksh

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.

______________________________________________
R-help at 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.

--
Robin Hankin
Uncertainty Analyst and Neutral Theorist,
National Oceanography Centre, Southampton
European Way, Southampton SO14 3ZH, UK
  tel  023-8059-7743