R: geco distance matrix

geco {prabclus} | R Documentation

## geco distance matrix

### Description

Computes geco distances between the columns of a 0-1-matrix, based on a distance matrix between regions (usually, but not necessarily, this is a geographical distance).

### Usage

    geco(regmat,geodist=as.dist(matrix(as.integer(!diag(nrow(regmat))))),
                       transform="piece",
                       tf=0.1,
                       countmode=ncol(regmat)+1)

### Arguments

`regmat` | 0-1-matrix. Columns are species, rows are regions.
`geodist` | `dist`-object or symmetric non-negative matrix. Geographical distances between regions.
`transform` | transformation applied to the distances before computation of geco coefficient, see details. "piece" means piecewise linear, namely distance/(`tf`*maximum distance) if distance<`tf`*maximum distance, and 1 otherwise, "log" means `log((tf*distance)+1)`, "sqrt" means `sqrt(tf*distance)`, "none" means no transformation.
`tf` | tuning constant for transformation. See `transform`.
`countmode` | optional positive integer. Every 'countmode' algorithm runs 'geco' shows a message.

### Details

The geco distance between two species is 0.5*(mean distance between region where species 1 is present and closest region where species 2 is present plus mean distance between region where species 2 is present and closest region where species 1 is present). 'closest' to a region could be the regions itself. It is recommended (Hennig and Hausdorf, 2006) to transform the distances first, because the differences between large distances are usually not meaningful or at least much less meaningful than differences between small distances for dissimilarity measurement between species ranges. See parameter `transform`.

If the between-regions distance is 1 for all pairs of non-equal regions, the geco distance degenerates to the Kulczynski distance, see `kulczynski`.

### Value

A symmetrical matrix of geco distances.

### Author(s)

Christian Hennig chrish@stats.ucl.ac.uk http://www.homepages.ucl.ac.uk/~ucakche

### References

Hennig, C. and Hausdorf, B. (2006) A robust distance coefficient between distribution areas incorporating geographic distances. Systematic Biology 55, 170-175.

### See Also

`kulczynski`

### Examples

    options(digits=4)
    data(kykladspecreg)
    data(waterdist)
    geco(t(kykladspecreg),waterdist)

[Package prabclus version 2.2-6 Index]