/*
 * 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.descriptive.moment;

import java.io.Serializable;
import java.util.Arrays;

import org.apache.commons.math.DimensionMismatchException;

/**
 * Returns the arithmetic mean of the available vectors.
 * 
 * @since 1.2
 * @version $Revision$ $Date$
 */
public class VectorialMean implements Serializable {

	/** Serializable version identifier */
	private static final long serialVersionUID = 8223009086481006892L;

	/** Means for each component. */
	private Mean[] means;

	/**
	 * Constructs a VectorialMean.
	 * 
	 * @param dimension
	 *            vectors dimension
	 */
	public VectorialMean(int dimension) {
		means = new Mean[dimension];
		for (int i = 0; i < dimension; ++i) {
			means[i] = new Mean();
		}
	}

	/**
	 * Add a new vector to the sample.
	 * 
	 * @param v
	 *            vector to add
	 * @exception DimensionMismatchException
	 *                if the vector does not have the right dimension
	 */
	public void increment(double[] v) throws DimensionMismatchException {
		if (v.length != means.length) {
			throw new DimensionMismatchException(v.length, means.length);
		}
		for (int i = 0; i < v.length; ++i) {
			means[i].increment(v[i]);
		}
	}

	/**
	 * Get the mean vector.
	 * 
	 * @return mean vector
	 */
	public double[] getResult() {
		double[] result = new double[means.length];
		for (int i = 0; i < result.length; ++i) {
			result[i] = means[i].getResult();
		}
		return result;
	}

	/**
	 * Get the number of vectors in the sample.
	 * 
	 * @return number of vectors in the sample
	 */
	public long getN() {
		return (means.length == 0) ? 0 : means[0].getN();
	}

	/** {@inheritDoc} */
	@Override
	public int hashCode() {
		final int prime = 31;
		int result = 1;
		result = prime * result + Arrays.hashCode(means);
		return result;
	}

	/** {@inheritDoc} */
	@Override
	public boolean equals(Object obj) {
		if (this == obj)
			return true;
		if (obj == null)
			return false;
		if (!(obj instanceof VectorialMean))
			return false;
		VectorialMean other = (VectorialMean) obj;
		if (!Arrays.equals(means, other.means))
			return false;
		return true;
	}

}