lower.to.upper.tri.inds
Permute Indices for Triangular Matrices
Description
Compute index vectors for extracting or reordering of lower or upper triangular matrices that are stored as contiguous vectors.
Usage
lower.to.upper.tri.inds(n) upper.to.lower.tri.inds(n)
Arguments
n | integer larger than 1. |
Value
integer vector containing a permutation of 1:N
where N = n(n-1)/2.
See Also
upper.tri
, lower.tri
with a related purpose.
Examples
m5 <- matrix(NA,5,5) m <- m5; m[lower.tri(m)] <- upper.to.lower.tri.inds(5); m m <- m5; m[upper.tri(m)] <- lower.to.upper.tri.inds(5); m stopifnot(lower.to.upper.tri.inds(2) == 1, lower.to.upper.tri.inds(3) == 1:3, upper.to.lower.tri.inds(3) == 1:3, sort(upper.to.lower.tri.inds(5)) == 1:10, sort(lower.to.upper.tri.inds(6)) == 1:15)
Copyright (©) 1999–2012 R Foundation for Statistical Computing.
Licensed under the GNU General Public License.