/**
* calculate the dunn index between two clusters
*
* @param clusters clusters
* @param dataset dataset
* @return dunn index
*/
public double calculateDunnIndex() {
double minDI = Double.MAX_VALUE;
for (int i = 0; i < clusters.size(); i++) {
Cluster ci = clusters.get(i);
if (!ci.getIsActive()) continue;
if (ci.getPointsIDs().size() < 30) continue;
for (int j = 0; j < clusters.size(); j++) {
Cluster cj = clusters.get(j);
if (ci.getID() == cj.getID() || !cj.getIsActive()) continue;
if (cj.getPointsIDs().size() < 30) continue;
double minDistBetCiCj = calculateMinDistanceBetweenTwoClusters(ci, cj);
double DIij = minDistBetCiCj / this.maxClusterSize;
if (DIij < minDI) {
minDI = DIij;
}
}
}
return minDI;
}
