symmetric matrix on both diagonals
On Apr 21, 2012, at 1:13 AM, Petr Savicky wrote:
On Fri, Apr 20, 2012 at 10:52:47AM -0400, David Winsemius wrote:
On Apr 20, 2012, at 7:05 AM, Petr Savicky wrote:
On Fri, Apr 20, 2012 at 03:03:40AM -0700, juliane0212 wrote:
I'm having some problems computing a matrix being symmetric on
both
diagonals.
Does anyone know a way to get from this matrix
M <- matrix(c(1,0,0,0,2,7,0,0,3,4,0,0,6,0,0,0), ncol=4)
to this one
M_final <- matrix(c(1,2,3,6,2,7,4,3,3,4,7,2,6,3,2,1),
ncol=4)
Hi. Try the following. M[row(M) > col(M)] <- t(M)[row(M) > col(M)] n <- nrow(M) M[row(M) + col(M) > n + 1] <- M[n:1, n:1][row(M) + col(M) > n + 1] all(M == M_final) [1] TRUE
How about?
M[3:4, ] <- rev(M[1:2,]) M
[,1] [,2] [,3] [,4] [1,] 1 2 3 6 [2,] 2 7 4 3 [3,] 3 4 7 2 [4,] 6 3 2 1
Hi. I am not sure, which matrix did you start from.
You are right. I misunderstood the requested task. (...and then used the wrong starting matrix.) Sorry for the noise.
David. > If we start > from the original matrix, then we get > > M <- matrix(c(1,0,0,0,2,7,0,0,3,4,0,0,6,0,0,0), ncol=4) > M[3:4, ] <- rev(M[1:2,]) > M > > [,1] [,2] [,3] [,4] > [1,] 1 2 3 6 > [2,] 0 7 4 0 > [3,] 0 4 7 0 > [4,] 6 3 2 1 > > where the components 2 and 3 have two and not four copies. > > Petr. > > ______________________________________________ > R-help at 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. David Winsemius, MD West Hartford, CT