extract half a matrix
On Thu, 22 May 2003, Tord Snall wrote:
Dear all,
I'm new to matrix operations in R. I couln't find a solution to the
following problem among earlier help mails or in An introd to R, I guess
because the question is really basic.
I want to extract all above the diagonal, i.e. from
1 2 3 4
1 0 26 49 49
2 26 0 44 40
3 49 44 0 21
4 49 40 21 0
In addition to the solution suggested by other people there are built-in functions upper.tri and lower.tri for doing this sort of thing, so x[upper.tri(x)] -thomas