/**
* 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.similarity.ItemSimilarity;
import org.apache.mahout.cf.taste.impl.model.GenericItem;
import org.apache.mahout.cf.taste.model.DataModel;
import org.apache.mahout.cf.taste.model.Item;
import org.apache.mahout.cf.taste.model.User;
import java.util.ArrayList;
import java.util.List;
/**
* <p>Tests {@link GenericItemSimilarity}.</p>
*/
public final class GenericItemSimilarityTest extends SimilarityTestCase {
public void testSimple() {
Item item1 = new GenericItem<String>("1");
Item item2 = new GenericItem<String>("2");
Item item3 = new GenericItem<String>("3");
Item item4 = new GenericItem<String>("4");
List<GenericItemSimilarity.ItemItemSimilarity> similarities =
new ArrayList<GenericItemSimilarity.ItemItemSimilarity>(4);
similarities.add(new GenericItemSimilarity.ItemItemSimilarity(item1, item2, 0.5));
similarities.add(new GenericItemSimilarity.ItemItemSimilarity(item2, item1, 0.6));
similarities.add(new GenericItemSimilarity.ItemItemSimilarity(item1, item1, 0.5));
similarities.add(new GenericItemSimilarity.ItemItemSimilarity(item1, item3, 0.3));
GenericItemSimilarity itemCorrelation = new GenericItemSimilarity(similarities);
assertEquals(1.0, itemCorrelation.itemSimilarity(item1, item1));
assertEquals(0.6, itemCorrelation.itemSimilarity(item1, item2));
assertEquals(0.6, itemCorrelation.itemSimilarity(item2, item1));
assertEquals(0.3, itemCorrelation.itemSimilarity(item1, item3));
assertTrue(Double.isNaN(itemCorrelation.itemSimilarity(item3, item4)));
}
public void testFromCorrelation() throws Exception {
User user1 = getUser("test1", 1.0, 2.0);
User user2 = getUser("test2", 2.0, 5.0);
User user3 = getUser("test3", 3.0, 6.0);
DataModel dataModel = getDataModel(user1, user2, user3);
ItemSimilarity otherSimilarity = new PearsonCorrelationSimilarity(dataModel);
ItemSimilarity itemSimilarity = new GenericItemSimilarity(otherSimilarity, dataModel);
assertCorrelationEquals(1.0,
itemSimilarity.itemSimilarity(dataModel.getItem("0"), dataModel.getItem("0")));
assertCorrelationEquals(0.960768922830523,
itemSimilarity.itemSimilarity(dataModel.getItem("0"), dataModel.getItem("1")));
}
}