On 2010-04-30 15:26, Nicholas Andrews wrote:
Here's an easy question: I'd like to convert a symmetric matrix to a
vector composed of the upper.tri() part of it plus the diagonal, and
convert it back again. What's the best way to achieve this? I'm
wondering if there are some built in functions to do this easily. I
can encode fine:
v<- c(diag(A),A[upper.tri(A)])
but I don't see an easy way to recover A from v without loops. Any tips?
To (re)create a symmetric matrix, use A + t(A):
If vd is diag(A) part of v and vu is the rest of v, and
let's take A to be 4-by-4, then
A <- matrix(0, 4, 4)
A[upper.tri(A)] <- vu
A <- A + t(A)
diag(A) <- vd
A
-Peter Ehlers
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--
Peter Ehlers
University of Calgary
______________________________________________
R-help@r-project.org mailing list
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PLEASE do read the posting guide http://www.R-project.org/posting-guide.html
and provide commented, minimal, self-contained, reproducible code.
