coef.hclust {cluster}R Documentation

Agglomerative Coefficient for 'hclust' Objects


Computes the “agglomerative coefficient”, measuring the clustering structure of the dataset.

For each observation i, denote by m(i) its dissimilarity to the first cluster it is merged with, divided by the dissimilarity of the merger in the final step of the algorithm. The agglomerative coefficient is the average of all 1 - m(i). It can also be seen as the average width (or the percentage filled) of the banner plot.

Because it grows with the number of observations, this measure should not be used to compare datasets of very different sizes.


coef.hclust(object, ...)
## S3 method for class 'hclust':
coef(object, ...)
## S3 method for class 'twins':
coef(object, ...)


object an object of class "hclust" or "twins", i.e., typically the result of hclust(.),agnes(.), or diana(.).
Since coef.hclust only uses object$heights, and object$merge, object can be any list-like object with appropriate merge and heights components.
... currently unused potential further arguments


a number specifying the agglomerative (or divisive for diana objects) coefficient as defined by Kaufman and Rousseeuw, see agnes.object $ ac or diana.object $ dc.


aa <- agnes(agriculture)
coef(aa) # really just extracts aa$ac
coef(as.hclust(aa))# recomputes

[Package cluster version 1.9.8 Index]