ade4 (version 1.01)

cailliez: Transformation to make Euclidean a distance matrix

Description

This function computes the smallest positive constant that makes Euclidean a distance matrix and applies it.

Usage

cailliez(distmat, print = FALSE)

Arguments

distmat

an object of class dist

print

if TRUE, prints the eigenvalues of the matrix

Value

• an object of class 'dist' containing an Euclidean distance matrix.

References

Cailliez, F. (1983) The analytical solution of the additive constant problem. Psychometrika, 48, 305--310. Legendre, P. and Anderson, M.J. (1999) Distance-based redundancy analysis: testing multispecies responses in multifactorial ecological experiments. Ecological Monographs, 69, 1--24. Legendre, P., and Legendre, L. (1998) Numerical ecology, 2nd English edition edition. Elsevier Science BV, Amsterdam. From the DistPCoa program of P. Legendre et M.J. Anderson http://www.fas.umontreal.ca/BIOL/Casgrain/en/labo/distpcoa.html

Examples

library(mva)
data(capitales)
d0 <- as.dist(capitales$df)
is.euclid(d0) # FALSE
d1 <- cailliez(d0, TRUE)
# Cailliez constant = 2429.87867 
is.euclid(d1) # TRUE
plot(d0, d1)
abline(lm(unclass(d1)~unclass(d0)))
print(coefficients(lm(unclass(d1)~unclass(d0))), dig = 8) # d1 = d + Cte
is.euclid(d0 + 2428) # FALSE
is.euclid(d0 + 2430) # TRUE the smallest constant