ade4 (version 1.7-19)

is.euclid: Is a Distance Matrix Euclidean?

Description

Confirmation of the Euclidean nature of a distance matrix by the Gower's theorem.
is.euclid is used in summary.dist.

Usage

is.euclid(distmat, plot = FALSE, print = FALSE, tol = 1e-07)
# S3 method for dist
summary(object, ...)

Value

returns a logical value indicating if all the eigenvalues are positive or equal to zero

Arguments

distmat

an object of class 'dist'

plot

a logical value indicating whether the eigenvalues bar plot of the matrix of the term \(-\frac{1}{2} {d_{ij}^2}\) centred by rows and columns should be diplayed

print

a logical value indicating whether the eigenvalues of the matrix of the term \(-\frac{1}{2} {d_{ij}^2}\) centred by rows and columns should be printed

tol

a tolerance threshold : an eigenvalue is considered positive if it is larger than -tol*lambda1 where lambda1 is the largest eigenvalue.

object

an object of class 'dist'

...

further arguments passed to or from other methods

Author

Daniel Chessel
Stéphane Dray

References

Gower, J.C. and Legendre, P. (1986) Metric and Euclidean properties of dissimilarity coefficients. Journal of Classification, 3, 5--48.

Examples

w <- matrix(runif(10000), 100, 100)
w <- dist(w)
summary(w)
is.euclid (w) # TRUE
w <- quasieuclid(w) # no correction need in: quasieuclid(w)
w <- lingoes(w) # no correction need in: lingoes(w)
w <- cailliez(w) # no correction need in: cailliez(w)
rm(w)