is.euclid {ade4} | R Documentation

## 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.
mat2dist and dist2mat are local copies of as.dist and as.matrix.dist of mva.

### Usage

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

### Arguments

`distmat` | an object of class 'dist'
`plot` | a logical value indicating whether the eigenvalues bar plot of the matrix of the term -1/2 dijē centred by rows and columns should be diplayed
`print` | a logical value indicating whether the eigenvalues of the matrix of the term -1/2 dijē 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

### Value

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

### Author(s)

Daniel Chessel chessel@biomserv.univ-lyon1.fr

### 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)

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