clusteval (version 0.1)

comembership: Calculates the comemberships of all pairs of a vector of clustering labels.

Description

For a set of clustering labels, this function computes the comembership of all pairs of observations. Basically, two observations are said to be comembers if they are clustered together.

Usage

comembership(labels)

Arguments

labels

a vector of n clustering labels

Value

a vector of choose(n, 2) comembership bits

Details

Tibshirani and Walther (2005) use the term 'co-membership', which we shorten to 'comembership'. Some authors instead use the terms 'connectivity' or 'co-occurrence'.

We use the Rcpp package to improve the runtime speed of this function.

References

Tibshirani, R. and Walther, G. (2005), Cluster Validation by Prediction Strength, _Journal of Computational and Graphical Statistics_, 14, 3, 511-528. http://amstat.tandfonline.com/doi/abs/10.1198/106186005X59243.

Examples

# We generate K = 3 labels for each of n = 10 observations and compute the
# comembership for all 'n choose 2' pairs.
set.seed(42)
K <- 3
n <- 10
labels <- sample.int(K, n, replace = TRUE)
comembership_out <- comembership(labels)
comembership_out

# Notice that the number of comemberships is 'n choose 2'.
length(comembership_out) == choose(n, 2)