/*
 * Copyright 2004 The Apache Software Foundation.
 * 
 * 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.apache.commons.math.stat.mining;

import java.util.Arrays;
import java.util.Set;
import java.util.TreeSet;

/**
 * Concrete class of Ranking Algorithm, who is responsible for ranking an array of data.
 * This class handles ties, or duplicate raw data, by assigning the all duplicate data the
 * same rank as the corresponding distinct value. For instance if we pass in the following list,
 * {1, 4, 2, 2, 1}, we would expect the Ranking Algorithm to return an array of ranks {1, 3, 2, 2, 1}.
 * This shows that all ties, of a raw value, are given the same rank.
 */
public class TiesEquivalentRank implements RankingAlgorithm{
    
    /**
     * Ranks an array of data, while all ties of a given value are assigned an equal rank.
     * 
     *  @param data Input array of raw data to be ranked.
     */
    public double[] rank(double[] data) {
        /*
         * simple rank algorithm
         * 1. Separate data
         *  a. Distinct values in set.
         * 2. Order set
         * 3. Itertate through intial data, grabbing index from set 
         */
        
        //separate data, add only distinct values to the set
        Set dataSet = new TreeSet();
        for(int i=0; i<data.length; i++) {
            dataSet.add(new Double(data[i]));
        }
        
        //order set, easier to do in an array
        Object [] dataArray = dataSet.toArray();
        Arrays.sort(dataArray);
       
        double [] ranks = new double[data.length];
        
        //find index in double array for matching data
        for(int i=0; i<data.length; i++) {
            Double desiredDouble = new Double(data[i]);
            int rank = Arrays.binarySearch(dataArray, desiredDouble) + 1;
            ranks[i] = rank;
        }
           
        return ranks;
    }
}