Split Matrix by Clusters and Return Lower Triangular Parts as Vector

Split a matrix into block diagonal sub matrices according to clusters and combine the lower triangular parts into a vector

lower.tri.vector(x, cluster = rep(1, nrow(x)), diag = FALSE)

Arguments

x	a square matrix
cluster	numeric or factor. Is used to identify the sub-matrices of x from which the lower triangular parts are extracted. Defaults to the full matrix.
diag	logical. Should the diagonal be included?

Value

Returns a numeric vector containing the elements of the lower triangular sub matrices.

See also

lower.tri

Examples

m <- matrix(1:64, ncol=8)
cluster <- c(1, 1, 1, 1, 2, 2, 3, 3)
lower.tri.vector(m, cluster)
#> [1]  2  3  4 11 12 20 38 56