/*
* chombo: Hadoop Map Reduce utility
* Author: Pranab Ghosh
*
* Licensed 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.chombo.util;
import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;
import java.util.Map;
/**
* Integer valued distribution
* @author pranab
*
*/
public class NumericalSampler {
private Map<Integer, Double> distrbutions = new HashMap<Integer, Double>();
private List<Pair<Integer, Double>> ranges = new ArrayList<Pair<Integer, Double>>();
private double maxRange;
private int binWidth;
public void initialize() {
distrbutions.clear();
ranges.clear();
}
public NumericalSampler(int binWidth) {
super();
this.binWidth = binWidth;
}
/**
* @param key
* @param value
*/
public void add(Integer key, Double value) {
distrbutions.put(key, value);
ranges.clear();
}
/**
* @return
*/
public int sample() {
Integer sampled = null;
if (ranges.isEmpty()) {
double upperBound = 0;
for (Integer key : distrbutions.keySet()) {
upperBound += distrbutions.get(key);
ranges.add(new Pair<Integer, Double>(key, upperBound));
}
maxRange = upperBound;
}
double rand = Math.random() * maxRange;
for (Pair<Integer, Double> item : ranges) {
if (rand < item.getRight()) {
sampled = item.getLeft();
}
}
//select randomly within bin
int randInt = (int)Math.random() * binWidth;
sampled += randInt - binWidth / 2;
return sampled;
}
}