lower triangle can be obtained by
A[row(A)>col(A)]
url: www.econ.uiuc.edu/~roger Roger Koenker email [EMAIL PROTECTED] Department of Economics vox: 217-333-4558 University of Illinois fax: 217-244-6678 Champaign, IL 61820
On Nov 25, 2004, at 11:15 AM, John wrote:
Hello R-users,
I have a symmetric matrix of numerical values and I want to obtain those values in the upper or lower triangle of the matrix in a vector. I tried to do the job by using two for-loops but it doens't seem to be a clever way, and I'd like to know a more efficient code for a large matrix of thousands of rows and columns. Below is my code for your reference.
Thanks a lot.
John
####################
# mtx.sym is a symmetric matrix
my.ftn <- function(size_mtx, mtx) {+ my.vector <- c() + for ( i in 1:size_mtx ) { + cat(".") + for ( j in 1:size_mtx ) { + if ( upper.tri(mtx)[i,j] ) { + my.vector <- c(my.vector, mtx[i,j]) + }}} + cat("\n") + }# if I have a matrix, mtx.sym, of 100x100
my.ftn(100, mtx.sym)
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