[R] generating symmetric matrices

Ben Bolker bolker at ufl.edu
Mon Jul 30 22:15:46 CEST 2007

Gregory Gentlemen <gregory_gentlemen <at> yahoo.ca> writes:

> Greetings,
> I have a seemingly simple task which I have not been able to solve today. I
want to construct a symmetric
> matrix of arbtriray size w/o using loops. The following I thought would do it:

p <- 6
Rmat <- diag(p)
vals <- rnorm(p*(p-1)/2)
Rmat[lower.tri(Rmat)] <- vals
Rmat[upper.tri(Rmat)] <- t(Rmat)[upper.tri(Rmat)]

  appears to work.

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