package org.apache.mahout.math.hadoop.stats;
/**
* 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.
*/
import org.apache.hadoop.io.DoubleWritable;
import org.apache.hadoop.io.IntWritable;
import org.apache.hadoop.mapreduce.Reducer;
import java.io.IOException;
public class StandardDeviationCalculatorReducer extends
Reducer<IntWritable, DoubleWritable, IntWritable, DoubleWritable> {
@Override
protected void reduce(IntWritable key, Iterable<DoubleWritable> values,
Context context) throws IOException, InterruptedException {
double sum = 0.0;
for (DoubleWritable value : values) {
sum += value.get();
}
context.write(key, new DoubleWritable(sum));
}
}