is.diagonal.matrix {matrixcalc}

Test for diagonal square matrix

Description

This function returns TRUE if the given matrix argument x is a square numeric matrix and that the off-diagonal elements are close to zero in absolute value to within the given tolerance level. Otherwise, a FALSE value is returned.

Usage

is.diagonal.matrix(x, tol = 1e-08)

Arguments

x

a numeric square matrix

tol

a numeric tolerance level usually left out

Value

A TRUE or FALSE value.

Author(s)

Frederick Novomestky [e-mail]

References

Bellman, R. (1987). Matrix Analysis, Second edition, Classics in Applied Mathematics, Society for Industrial and Applied Mathematics.

Horn, R. A. and C. R. Johnson (1990). Matrix Analysis, Cambridge University Press.

Examples

A <- diag( 1, 3 )
is.diagonal.matrix( A )
B <- matrix( c( 1, 2, 3, 4 ), nrow=2, byrow=TRUE )
is.diagonal.matrix( B )
C <- matrix( c( 1, 0, 0, 0 ), nrow=2, byrow=TRUE )
is.diagonal.matrix( C )