/**
* 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.math.stats.entropy;
import com.google.common.io.Closeables;
import org.apache.hadoop.conf.Configuration;
import org.apache.hadoop.fs.FileSystem;
import org.apache.hadoop.fs.Path;
import org.apache.hadoop.io.SequenceFile;
import org.apache.hadoop.io.Text;
import org.apache.hadoop.util.ToolRunner;
import org.apache.mahout.common.MahoutTestCase;
import org.junit.Test;
public final class InformationGainTest extends MahoutTestCase {
@Test
public void testInformationGain() throws Exception {
Configuration configuration = new Configuration();
FileSystem fileSystem = FileSystem.get(configuration);
Path input = getTestTempFilePath("input");
// create input
String[] keys = { "Math", "History", "CS", "Math", "Math", "CS", "History", "Math" };
String[] values = { "Yes", "No", "Yes", "No", "No", "Yes", "No", "Yes" };
SequenceFile.Writer writer = new SequenceFile.Writer(fileSystem, configuration, input, Text.class, Text.class);
try {
for (int i = 0; i < keys.length; i++) {
writer.append(new Text(keys[i]), new Text(values[i]));
}
} finally {
Closeables.closeQuietly(writer);
}
// run the job
InformationGain job = new InformationGain();
String[] args = { "-i", input.toString() };
ToolRunner.run(job, args);
// check the output
assertEquals(1.0, job.getEntropy(), EPSILON);
assertEquals(0.5, job.getConditionalEntropy(), EPSILON);
assertEquals(0.5, job.getInformationGain(), EPSILON);
}
}