TanimotoCoefficientSimilarityTest.java

/**
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You under the Apache License, Version 2.0
 * (the "License"); you may not use this file except in compliance with
 * the License.  You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package org.apache.mahout.cf.taste.impl.similarity;

import org.apache.mahout.cf.taste.model.DataModel;
import org.junit.Test;

/** <p>Tests {@link TanimotoCoefficientSimilarity}.</p> */
public final class TanimotoCoefficientSimilarityTest extends SimilarityTestCase {

  @Test
  public void testNoCorrelation() throws Exception {
    DataModel dataModel = getDataModel(
            new long[] {1, 2},
            new Double[][] {
                    {null, 2.0, 3.0},
                    {1.0},
            });
    double correlation = new TanimotoCoefficientSimilarity(dataModel).userSimilarity(1, 2);
    assertCorrelationEquals(Double.NaN, correlation);
  }

  @Test
  public void testFullCorrelation1() throws Exception {
    DataModel dataModel = getDataModel(
            new long[] {1, 2},
            new Double[][] {
                    {1.0},
                    {1.0},
            });
    double correlation = new TanimotoCoefficientSimilarity(dataModel).userSimilarity(1, 2);
    assertCorrelationEquals(1.0, correlation);
  }

  @Test
  public void testFullCorrelation2() throws Exception {
    DataModel dataModel = getDataModel(
            new long[] {1, 2},
            new Double[][] {
                    {1.0, 2.0, 3.0},
                    {1.0},
            });
    double correlation = new TanimotoCoefficientSimilarity(dataModel).userSimilarity(1, 2);
    assertCorrelationEquals(0.3333333333333333, correlation);
  }

  @Test
  public void testCorrelation1() throws Exception {
    DataModel dataModel = getDataModel(
            new long[] {1, 2},
            new Double[][] {
                    {null, 2.0, 3.0},
                    {1.0, 1.0},
            });
    double correlation = new TanimotoCoefficientSimilarity(dataModel).userSimilarity(1, 2);
    assertEquals(0.3333333333333333, correlation, EPSILON);
  }

  @Test
  public void testCorrelation2() throws Exception {
    DataModel dataModel = getDataModel(
            new long[] {1, 2},
            new Double[][] {
                    {null, 2.0, 3.0, 1.0},
                    {1.0, 1.0, null, 0.0},
            });
    double correlation = new TanimotoCoefficientSimilarity(dataModel).userSimilarity(1, 2);
    assertEquals(0.5, correlation, EPSILON);
  }

  @Test
  public void testRefresh() {
    // Make sure this doesn't throw an exception
    new TanimotoCoefficientSimilarity(getDataModel()).refresh(null);
  }

  @Test
  public void testReturnNaNDoubleWhenNoSimilaritiesForTwoItems() throws Exception {
	  DataModel dataModel = getDataModel(
            new long[] {1, 2},
            new Double[][] {
                    {null, null, 3.0},
                    {1.0, 1.0, null},
            });  
	  Double similarity = new TanimotoCoefficientSimilarity(dataModel).itemSimilarity(1, 2);
	  assertEquals(Double.NaN, similarity, EPSILON);
  }
  
  @Test
  public void testItemsSimilarities() throws Exception {
	  DataModel dataModel = getDataModel(
	            new long[] {1, 2},
	            new Double[][] {
	                    {2.0, null, 2.0},
	                    {1.0, 1.0, 1.0},
	            });  
	  TanimotoCoefficientSimilarity tCS = new TanimotoCoefficientSimilarity(dataModel);
	  assertEquals(0.5, tCS.itemSimilarity(0, 1), EPSILON);
	  assertEquals(1, tCS.itemSimilarity(0, 2), EPSILON);
	  
	  double[] similarities = tCS.itemSimilarities(0, new long [] {1, 2});
	  assertEquals(0.5, similarities[0], EPSILON);
	  assertEquals(1, similarities[1], EPSILON);
  }
  
}