Singular matrix

'x' is a rank 5 matrix from which you want to create a rank 10 
crossproduct! Try the following instead:

x <- array(rnorm(100 * nitems, 3, 3), c(100, nitems))
sigma <- crossprod(x)

I hope it helps.

Best,
Dimitris

----
Dimitris Rizopoulos
Ph.D. Student
Biostatistical Centre
School of Public Health
Catholic University of Leuven

Address: Kapucijnenvoer 35, Leuven, Belgium
Tel: +32/(0)16/336899
Fax: +32/(0)16/337015
Web: http://www.med.kuleuven.be/biostat/
     http://www.student.kuleuven.be/~m0390867/dimitris.htm


----- Original Message ----- 
From: "Marc Bernard" <bernarduse1 at yahoo.fr>
To: <r-help at stat.math.ethz.ch>
Sent: Thursday, October 06, 2005 3:11 PM
Subject: [R] Singular matrix

Dear All,

I have written the  following programs  to find a non-singular 
(10*10) covariance matrix.
Here  is the program:

nitems <- 10

x <- array(rnorm(5*nitems,3,3), c(5,nitems))

sigma <- t(x)%*%x

inverse <- try(solve(sigma), TRUE)



while(inherits(inverse, "try-error"))

{

x <- array(rnorm(5*nitems,3,3), c(5,nitems))

sigma <- t(x)%*%x

inverse <- try(solve(sigma), TRUE)

}



The loop doesn't stop ...  This means that  no "non-singular" matrix 
was found!!!

some thing wrong !!



Thanks a lot for any reply



Bernard









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