src/org/apache/pig/impl/builtin/FindQuantiles.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.pig.impl.builtin;

import java.io.IOException;
import java.util.Iterator;

import org.apache.pig.EvalFunc;
import org.apache.pig.data.DataBag;
import org.apache.pig.data.Tuple;


public class FindQuantiles extends EvalFunc<DataBag>{
    
    /**
     * first field in the input tuple is the number of quantiles to generate
     * second field is the *sorted* bag of samples
     */
    
    @Override
    public void exec(Tuple input, DataBag output) throws IOException {
        int numQuantiles = input.getAtomField(0).numval().intValue();
        DataBag samples = input.getBagField(1);
        
        long numSamples = samples.size();
        
        long i=0, written = 0;
        Iterator<Tuple> iter = samples.iterator();
        while (iter.hasNext()){
            Tuple t = iter.next();
            if ((written + 1) * numSamples < i * (numQuantiles + 1)) {
                output.add(t);
                written++;
            }
            i++;
        }
    }
}