Find the trace of a square matrix

Hardly worth coding, if it didn't appear in so many formulae in psychometrics, the trace of a (square) matrix is just the sum of the diagonal elements.

tr(m)

Arguments

m

A square matrix

Details

The tr function is used in various matrix operations and is the sum of the diagonal elements of a matrix.

Value

The sum of the diagonal elements of a square matrix.
i.e. tr(m) <- sum(diag(m)).

Examples

 m <- matrix(1:16,ncol=4)
 m
#>      [,1] [,2] [,3] [,4]
#> [1,]    1    5    9   13
#> [2,]    2    6   10   14
#> [3,]    3    7   11   15
#> [4,]    4    8   12   16
 tr(m)
#> [1] 34