Matrix (version 0.999375-42)

pMatrix-class: Permutation matrices

Description

The "pMatrix" class is the class of permutation matrices, stored as 1-based integer permutation vectors.

Objects from the Class

Objects can be created by calls of the form new("pMatrix", ...) or by coercion from an integer permutation vector, see below.

Extends

Class "sparseMatrix" and "generalMatrix", directly.

Examples

(pm1 <- as(as.integer(c(2,3,1)), "pMatrix"))
t(pm1) # is the same as
solve(pm1)
pm1 %*% t(pm1) # check that the transpose is the inverse
stopifnot(all(diag(3) == as(pm1 %*% t(pm1), "matrix")),
          is.logical(as(pm1, "matrix")))

set.seed(11)
## random permutation matrix :
(p10 <- as(sample(10),"pMatrix"))

## Permute rows / columns of a numeric matrix :
(mm <- round(array(rnorm(3 * 3), c(3, 3)), 2))
mm %*% pm1
pm1 %*% mm
try(as(as.integer(c(3,3,1)), "pMatrix"))# Error: not a permutation

as(pm1, "ngTMatrix")
p10[1:7, 1:4] # gives an "ngTMatrix" (most economic!)