/*
 * 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.commons.math.stat.ranking;

/**
 * Interface representing a rank transformation.
 * 
 * @since 2.0
 * @version $Revision:$ $Date:$
 */
public interface RankingAlgorithm {
	/**
	 * <p>
	 * Performs a rank transformation on the input data, returning an array of
	 * ranks.
	 * </p>
	 * 
	 * <p>
	 * Ranks should be 1-based - that is, the smallest value returned in an
	 * array of ranks should be greater than or equal to one, rather than 0.
	 * Ranks should in general take integer values, though implementations may
	 * return averages or other floating point values to resolve ties in the
	 * input data.
	 * </p>
	 * 
	 * @param data
	 *            array of data to be ranked
	 * @return an array of ranks corresponding to the elements of the input
	 *         array
	 */
	double[] rank(double[] data);
}
