ArrayRankDouble.java

/*
 * Copyright (C) 2011 Jacquet Wong
 *
 * 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 com.musicg.math.rank;

public class ArrayRankDouble {

	/**
	 * Get the index position of maximum value the given array 
	 * @param array
	 * @return	index of the max value in array
	 */
	public int getMaxValueIndex(double[] array) {

		int index = 0;
		double max = Integer.MIN_VALUE;
		
		for (int i = 0; i < array.length; i++) {
			if (array[i] > max) {
				max = array[i];
				index = i;
			}
		}

		return index;
	}

	/**
	 * Get the index position of minimum value in the given array 
	 * @param array
	 * @return	index of the min value in array
	 */
	public int getMinValueIndex(double[] array) {

		int index = 0;
		double min = Integer.MAX_VALUE;

		for (int i = 0; i < array.length; i++) {
			if (array[i] < min) {
				min = array[i];
				index = i;
			}
		}

		return index;
	}

	/**
	 * Get the n-th value in the array after sorted
	 * @param array
	 * @param n
	 * @param ascending	is ascending order or not
	 * @return
	 */
	public double getNthOrderedValue(double[] array, int n, boolean ascending) {

		if (n > array.length) {
			n = array.length;
		}

		int targetindex;
		if (ascending) {
			targetindex = n;
		} else {
			targetindex = array.length - n;
		}

		// this value is the value of the numKey-th element
		double passValue = getOrderedValue(array, targetindex);

		return passValue;
	}

	private double getOrderedValue(double[] array, int index) {
		locate(array, 0, array.length - 1, index);
		return array[index];
	}

	// sort the partitions by quick sort, and locate the target index
	private void locate(double[] array, int left, int right, int index) {

		int mid = (left + right) / 2;
		// System.out.println(left+" to "+right+" ("+mid+")");

		if (right == left) {
			// System.out.println("* "+array[targetIndex]);
			// result=array[targetIndex];
			return;
		}

		if (left < right) {
			double s = array[mid];
			int i = left - 1;
			int j = right + 1;

			while (true) {
				while (array[++i] < s)
					;
				while (array[--j] > s)
					;
				if (i >= j)
					break;
				swap(array, i, j);
			}

			// System.out.println("2 parts: "+left+"-"+(i-1)+" and "+(j+1)+"-"+right);

			if (i > index) {
				// the target index in the left partition
				// System.out.println("left partition");
				locate(array, left, i - 1, index);
			} else {
				// the target index in the right partition
				// System.out.println("right partition");
				locate(array, j + 1, right, index);
			}
		}
	}

	private void swap(double[] array, int i, int j) {
		double t = array[i];
		array[i] = array[j];
		array[j] = t;
	}
}