Mahout: SpearmanCorrelationSimilarity : Compute User similarity

SpearmanCorrelationSimilarity is like PearsonCorrelationSimilarity, but compares relative ranking of preference values instead of preference values themselves. That is, each user's preferences are sorted and then assign a rank as their preference value, with 1 being assigned to the least preferred item.

Let’s say I had following input data.

customer.csv

1,4,3
1,7,2
1,8,2
1,10,1
2,3,2
2,4,3
2,6,3
2,7,1
2,9,1
3,0,3
3,3,2
3,4,1
3,8,3
3,9,1
4,2,5
4,3,4
4,7,3
4,9,2
5,4,5
5,6,4
5,7,1
5,8,3

1,4,3 means customer 1 like item 4 and rated it 3

import java.io.File;
import java.io.IOException;

import org.apache.mahout.cf.taste.common.TasteException;
import org.apache.mahout.cf.taste.impl.model.file.FileDataModel;
import org.apache.mahout.cf.taste.impl.similarity.SpearmanCorrelationSimilarity;
import org.apache.mahout.cf.taste.model.DataModel;

public class SpearmanCorrelationSimilarityEx {
 public static String dataFile = "/Users/harikrishna_gurram/customer.csv";

 public static void main(String args[]) throws IOException, TasteException {

  DataModel model = new FileDataModel(new File(dataFile));

  SpearmanCorrelationSimilarity similarity = new SpearmanCorrelationSimilarity(
    model);

  System.out.println("Similarity between user1 and user2 is "
    + similarity.userSimilarity(1, 2));

 }
}

Output

Similarity between user1 and user2 is 1.0

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