Another method that is based on the concept of dense and well-separated clusters is the Calinski-Harabasz index. To build it, we need first to define the inter cluster dispersion. If we have k clusters with their relative centroids and the global centroid, the inter-cluster dispersion (BCD) is defined as:
In the above expression, nk is the number of elements belonging to the cluster k, mu (the Greek letter in the formula) is the global centroid, and mui is the centroid of cluster i. The intracluster dispersion (WCD) is defined as:
The Calinski-Harabasz index is defined as the ratio between BCD(k) and WCD(k):
As we ...
