R: Test for diagonal square matrix

is.diagonal.matrix {matrixcalc} | R Documentation

## 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 fnovomes@poly.edu

### 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 )

[Package matrixcalc version 1.0-3 Index]