# is.euclid: Is a Distance Matrix Euclidean? In ade4: Analysis of Ecological Data: Exploratory and Euclidean Methods in Environmental Sciences

 is.euclid 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`.

### Usage

```is.euclid(distmat, plot = FALSE, print = FALSE, tol = 1e-07)
## S3 method for class 'dist'
summary(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 dij² centred by rows and columns should be diplayed `print` a logical value indicating whether the eigenvalues of the matrix of the term -1/2 dij² 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
Stéphane Dray stephane.dray@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)
```

ade4 documentation built on Nov. 2, 2022, 1:07 a.m.