[SOLVED] Clustering SSE measure calculation

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  nav Member Posts: 28 Contributor II

  January 2012

  I answer myself and share some piece of knowledge with you...
  
  To calculate the SSE measure I wrote a small script in the Execute Script Operator. The script is this;

  /**
  *	Author: N@v
  *	Version: 0.0.1
  *	Date: 11/01/2012
  *
  *	Description:
  *	This script permits to calculate the SSE measure of a given clustering coming out from a centroid-based clustering algorithm.
  *
  *	Input:
  *	input[0]: the example set of the clustering
  *	input[1]: the example set of the centroids
  *	input[2]: the cluster model of the cluster operator
  *
  *	Output:
  *	The SSE value of the clustering will be displayed in log consolle.
  **/
  
  import com.rapidminer.operator.clustering.ClusterModel;
  import com.rapidminer.operator.clustering.Cluster;
  
  ExampleSet clusteringSet = input[0];
  ExampleSet centroids = input[1];
  ClusterModel clustering = input[2];
  
  Double sum = new Double(0);
  centroids.remapIds();
  TreeMap<Integer,Example> centroidMap = new TreeMap<Integer, Example>();
  for (Example centroid : centroids) {
  	String key = centroid.getValueAsString(centroid.getAttributes().get("cluster"));
  	key = key.substring(8);	
  	Cluster cluster = clustering.getCluster(Integer.parseInt(key));
  
  	if (cluster.getNumberOfExamples() == 0) {
  		continue;
  	}
  	else {
  		Collection<Object> idsList = cluster.getExampleIds();
  		clusteringSet.remapIds();	
  		for (Object id : idsList) {
  			Example example = clusteringSet.getExampleFromId((Double) id);
  			distance = new Double(calculateEuclideanDistance(centroid, example));
  			sum += distance*distance;
  		}
  	}
  }
  operator.logNote("SSE: " + sum);
  
  
  Double calculateEuclideanDistance(Example a, Example b)
  {
  		Attribute[] atts = a.getAttributes().createRegularAttributeArray();
  		Double sum = new Double(0);
  		Double dist = new Double(0);
  		for (Attribute att : atts){
  			String attStr = att.getName();
  			Double aValue = new Double(a.getValue(a.getAttributes().get(attStr)));
  			Double bValue = new Double(b.getValue(b.getAttributes().get(attStr)));
  			Double difference = new Double(aValue - bValue);
  			sum += Math.pow(difference,2);
  		}
  		dist = Math.sqrt(sum);
  
  		return dist;
  }
  

  The script is very simple and at now it works only for centroid-based algorithm but I plan to adapt it to general case... it needs only to calculate the centroids by hand.
  
  If you have any comments or suggestions let me know.

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  Asmaa_Ali Member Posts: 1 Contributor I

  July 2019 edited July 2019

  Hello 
  I used the script but i got this error 
  "cannot cast object'cluster 0:..items cluster 1:..items Total number of items with class'com.rapidminer.operator.clustering.ClusterModel' to class 'com.rapidminer.example.ExampeSet'
  
  thanks

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