Trace of a matrix

Computes the trace of a matrix.

Usage

tr(x)

Arguments

x

a numeric matrix.

Details

tr computes the trace of a square matrix, i.e., the sum of its diagonal elements.

If the matrix is not square, tr returns NA.

References

Golub, van Loan, (1996); Matrix Computations, 3rd edition. Johns Hopkins University Press.

Examples

## Create Pascal Matrix:
   P = pascal(3)
   P
#>      [,1] [,2] [,3]
#> [1,]    1    1    1
#> [2,]    1    2    3
#> [3,]    1    3    6
  
## Trace:
   tr(P)                                  
#> [1] 9