On Sat, 2008-04-12 at 10:56 +0100, Rory Winston wrote: > Hi > > Does anyone know how I might pick out diagonal elements of a matrix using a > vector? > > If I create a matrix a: > > a <- matrix(c(1:16), 4, byrow=TRUE)
Not sure if this does all that you describe below, but: diag(a) and you can subset that to get the first 3 elements say: diag(a)[1:3] HTH G > > and I want to pick out the elements (1,1),(2,2),(3,3), or another arbitrary > diagonal (upper or lower), is there any way I can use a vector to do this? > So if I want a diagonal of size 3, I could create a vector like x <- c(0:2) > and then pick out a[1+x,1+x]? Currently, using a vector in this way gives me > a sub-matrix, as I get the cartesian product of the indexes (which is to be > expected, as I guess I am misusing the vector notion here). > > Anyone know how to do this? > > Cheers > Rory > > [[alternative HTML version deleted]] > > ______________________________________________ > 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. -- %~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~% Dr. Gavin Simpson [t] +44 (0)20 7679 0522 ECRC, UCL Geography, [f] +44 (0)20 7679 0565 Pearson Building, [e] gavin.simpsonATNOSPAMucl.ac.uk Gower Street, London [w] http://www.ucl.ac.uk/~ucfagls/ UK. WC1E 6BT. [w] http://www.freshwaters.org.uk %~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~% ______________________________________________ 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.