/*
 * 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.math3.stat.descriptive.summary;

import java.io.Serializable;

import org.apache.commons.math3.exception.MathIllegalArgumentException;
import org.apache.commons.math3.exception.NullArgumentException;
import org.apache.commons.math3.stat.descriptive.AbstractStorelessUnivariateStatistic;
import org.apache.commons.math3.util.MathUtils;


Returns the sum of the available values.

If there are no values in the dataset, then 0 is returned.
If any of the values are
NaN, then NaN is returned.

Note that this implementation is not synchronized. If
multiple threads access an instance of this class concurrently, and at least
one of the threads invokes the increment() or
clear() method, it must be synchronized externally.
/**
  * Returns the sum of the available values.
 * <p>
 * If there are no values in the dataset, then 0 is returned.
 * If any of the values are
 * <code>NaN</code>, then <code>NaN</code> is returned.</p>
 * <p>
 * <strong>Note that this implementation is not synchronized.</strong> If
 * multiple threads access an instance of this class concurrently, and at least
 * one of the threads invokes the <code>increment()</code> or
 * <code>clear()</code> method, it must be synchronized externally.</p>
 *
 */
public class Sum extends AbstractStorelessUnivariateStatistic implements Serializable {

    
Serializable version identifier /** Serializable version identifier */
    private static final long serialVersionUID = -8231831954703408316L;

    /** */
    private long n;

    
The currently running sum.
/**
     * The currently running sum.
     */
    private double value;

    
Create a Sum instance
/**
     * Create a Sum instance
     */
    public Sum() {
        n = 0;
        value = 0;
    }

    
Copy constructor, creates a new Sum identical to the original 
Params:
original – the Sum instance to copy
Throws:
NullArgumentException – if original is null/**
     * Copy constructor, creates a new {@code Sum} identical
     * to the {@code original}
     *
     * @param original the {@code Sum} instance to copy
     * @throws NullArgumentException if original is null
     */
    public Sum(Sum original) throws NullArgumentException {
        copy(original, this);
    }

    
{@inheritDoc}
/**
     * {@inheritDoc}
     */
    @Override
    public void increment(final double d) {
        value += d;
        n++;
    }

    
{@inheritDoc}
/**
     * {@inheritDoc}
     */
    @Override
    public double getResult() {
        return value;
    }

    
{@inheritDoc}
/**
     * {@inheritDoc}
     */
    public long getN() {
        return n;
    }

    
{@inheritDoc}
/**
     * {@inheritDoc}
     */
    @Override
    public void clear() {
        value = 0;
        n = 0;
    }

    
The sum of the entries in the specified portion of
the input array, or 0 if the designated subarray
is empty.

Throws MathIllegalArgumentException if the array is null.
Params:
values – the input array
begin – index of the first array element to include
length – the number of elements to include
Throws:
MathIllegalArgumentException – if the array is null or the array index
 parameters are not valid
Returns:
the sum of the values or 0 if length = 0/**
     * The sum of the entries in the specified portion of
     * the input array, or 0 if the designated subarray
     * is empty.
     * <p>
     * Throws <code>MathIllegalArgumentException</code> if the array is null.</p>
     *
     * @param values the input array
     * @param begin index of the first array element to include
     * @param length the number of elements to include
     * @return the sum of the values or 0 if length = 0
     * @throws MathIllegalArgumentException if the array is null or the array index
     *  parameters are not valid
     */
    @Override
    public double evaluate(final double[] values, final int begin, final int length)
    throws MathIllegalArgumentException {
        double sum = Double.NaN;
        if (test(values, begin, length, true)) {
            sum = 0.0;
            for (int i = begin; i < begin + length; i++) {
                sum += values[i];
            }
        }
        return sum;
    }

    
The weighted sum of the entries in the specified portion of
the input array, or 0 if the designated subarray
is empty.

Throws MathIllegalArgumentException if any of the following are true:
the values array is null
    
the weights array is null
    
the weights array does not have the same length as the values array
    
the weights array contains one or more infinite values
    
the weights array contains one or more NaN values
    
the weights array contains negative values
    
the start and length arguments do not determine a valid array


Uses the formula, 
   weighted sum = Σ(values[i] * weights[i])

Params:
values – the input array
weights – the weights array
begin – index of the first array element to include
length – the number of elements to include
Throws:
MathIllegalArgumentException – if the parameters are not valid
Returns:
the sum of the values or 0 if length = 0
Since:
2.1/**
     * The weighted sum of the entries in the specified portion of
     * the input array, or 0 if the designated subarray
     * is empty.
     * <p>
     * Throws <code>MathIllegalArgumentException</code> if any of the following are true:
     * <ul><li>the values array is null</li>
     *     <li>the weights array is null</li>
     *     <li>the weights array does not have the same length as the values array</li>
     *     <li>the weights array contains one or more infinite values</li>
     *     <li>the weights array contains one or more NaN values</li>
     *     <li>the weights array contains negative values</li>
     *     <li>the start and length arguments do not determine a valid array</li>
     * </ul></p>
     * <p>
     * Uses the formula, <pre>
     *    weighted sum = &Sigma;(values[i] * weights[i])
     * </pre></p>
     *
     * @param values the input array
     * @param weights the weights array
     * @param begin index of the first array element to include
     * @param length the number of elements to include
     * @return the sum of the values or 0 if length = 0
     * @throws MathIllegalArgumentException if the parameters are not valid
     * @since 2.1
     */
    public double evaluate(final double[] values, final double[] weights,
        final int begin, final int length) throws MathIllegalArgumentException {
        double sum = Double.NaN;
        if (test(values, weights, begin, length, true)) {
            sum = 0.0;
            for (int i = begin; i < begin + length; i++) {
                sum += values[i] * weights[i];
            }
        }
        return sum;
    }

    
The weighted sum of the entries in the the input array.

Throws MathIllegalArgumentException if any of the following are true:
the values array is null
    
the weights array is null
    
the weights array does not have the same length as the values array
    
the weights array contains one or more infinite values
    
the weights array contains one or more NaN values
    
the weights array contains negative values


Uses the formula, 
   weighted sum = Σ(values[i] * weights[i])

Params:
values – the input array
weights – the weights array
Throws:
MathIllegalArgumentException – if the parameters are not valid
Returns:
the sum of the values or Double.NaN if length = 0
Since:
2.1/**
     * The weighted sum of the entries in the the input array.
     * <p>
     * Throws <code>MathIllegalArgumentException</code> if any of the following are true:
     * <ul><li>the values array is null</li>
     *     <li>the weights array is null</li>
     *     <li>the weights array does not have the same length as the values array</li>
     *     <li>the weights array contains one or more infinite values</li>
     *     <li>the weights array contains one or more NaN values</li>
     *     <li>the weights array contains negative values</li>
     * </ul></p>
     * <p>
     * Uses the formula, <pre>
     *    weighted sum = &Sigma;(values[i] * weights[i])
     * </pre></p>
     *
     * @param values the input array
     * @param weights the weights array
     * @return the sum of the values or Double.NaN if length = 0
     * @throws MathIllegalArgumentException if the parameters are not valid
     * @since 2.1
     */
    public double evaluate(final double[] values, final double[] weights)
    throws MathIllegalArgumentException {
        return evaluate(values, weights, 0, values.length);
    }

    
{@inheritDoc}
/**
     * {@inheritDoc}
     */
    @Override
    public Sum copy() {
        Sum result = new Sum();
        // No try-catch or advertised exception because args are valid
        copy(this, result);
        return result;
    }

    
Copies source to dest.
Neither source nor dest can be null.
Params:
source – Sum to copy
dest – Sum to copy to
Throws:
NullArgumentException – if either source or dest is null/**
     * Copies source to dest.
     * <p>Neither source nor dest can be null.</p>
     *
     * @param source Sum to copy
     * @param dest Sum to copy to
     * @throws NullArgumentException if either source or dest is null
     */
    public static void copy(Sum source, Sum dest)
        throws NullArgumentException {
        MathUtils.checkNotNull(source);
        MathUtils.checkNotNull(dest);
        dest.setData(source.getDataRef());
        dest.n = source.n;
        dest.value = source.value;
    }

}