R: Average within-group distances for given groups

specgroups {prabclus} | R Documentation

## Average within-group distances for given groups

### Description

Generates average within-group distances (overall and group-wise) from a dissimilarity matrix and a given grouping.

### Usage

      specgroups(distmat,groupvector, groupinfo)

### Arguments

`distmat` | dissimilarity matrix or `dist`-object.
`groupvector` | integer vector. For every row of `distmat`, a number indicating the group membership.
`groupinfo` | list with components `lg` (levels of `groupvector`), `ng` (number of groups), `nsg` (vector of group sizes).

### Value

A list with parameters

`overall` | overall average within-groups dissimilarity.
`gr` | vector of group-wise average within-group dissimilarities (this will be `NaN` if the group size is only 1).

### Author(s)

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

### Examples

      options(digits=4)
      data(siskiyou)
      x <- prabinit(prabmatrix=siskiyou, neighborhood=siskiyou.nb,
                  distance="logkulczynski")
      groupvector <- as.factor(siskiyou.groups)
      ng <- length(levels(groupvector))
      lg <- levels(groupvector)
      nsg <- numeric(0)
        for (i in 1:ng) nsg[i] <- sum(groupvector==lg[i])
      groupinfo <- list(lg=lg,ng=ng,nsg=nsg)
      specgroups(x$distmat,groupvector,groupinfo)

[Package prabclus version 2.2-6 Index]