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;
	}