com.datatorrent.lib.statistics.MedianOperator Maven / Gradle / Ivy
/**
* 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 com.datatorrent.lib.statistics;
import java.util.ArrayList;
import java.util.Collections;
import com.datatorrent.api.DefaultInputPort;
import com.datatorrent.api.DefaultOutputPort;
import com.datatorrent.api.annotation.OperatorAnnotation;
import com.datatorrent.common.util.BaseOperator;
/**
* An implementation of BaseOperator that computes median of incoming data.
*
* Input Port(s) :
* data : Data values input port.
*
* Output Port(s) :
* median : Median output port.
*
* StateFull : Yes, value are aggregated over application window.
* Partitions : No, no will yield wrong results.
*
+
* @displayName Median
* @category Stats and Aggregations
* @tags median operator, number
* @since 0.3.4
*/
@OperatorAnnotation(partitionable = false)
public class MedianOperator extends BaseOperator
{
private ArrayList values;
/**
* Input data port that takes a number.
*/
public final transient DefaultInputPort data = new DefaultInputPort()
{
/**
* Computes sum and count with each tuple
*/
@Override
public void process(Number tuple)
{
values.add(tuple.doubleValue());
}
};
/**
* Output port that emits median of incoming data.
*/
public final transient DefaultOutputPort median = new DefaultOutputPort();
@Override
public void beginWindow(long arg0)
{
values = new ArrayList();
}
@Override
public void endWindow()
{
if (values.size() == 0) {
return;
}
if (values.size() == 1) {
median.emit(values.get(0));
return;
}
// median value
Collections.sort(values);
int medianIndex = values.size() / 2;
if (values.size() % 2 == 0) {
Double value = values.get(medianIndex - 1);
value = (value + values.get(medianIndex)) / 2;
median.emit(value);
} else {
median.emit(values.get(medianIndex));
}
}
}