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A Java's Collaborative Filtering library to carry out experiments in research of Collaborative Filtering based Recommender Systems. The library has been designed from researchers to researchers.

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/*
 * 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;

/**
 *  Reporting interface for basic univariate statistics.
 *
 */
public interface StatisticalSummary {

    /**
     * Returns the 
     * arithmetic mean  of the available values
     * @return The mean or Double.NaN if no values have been added.
     */
    double getMean();
    /**
     * Returns the variance of the available values.
     * @return The variance, Double.NaN if no values have been added
     * or 0.0 for a single value set.
     */
    double getVariance();
    /**
     * Returns the standard deviation of the available values.
     * @return The standard deviation, Double.NaN if no values have been added
     * or 0.0 for a single value set.
     */
    double getStandardDeviation();
    /**
     * Returns the maximum of the available values
     * @return The max or Double.NaN if no values have been added.
     */
    double getMax();
    /**
    * Returns the minimum of the available values
    * @return The min or Double.NaN if no values have been added.
    */
    double getMin();
    /**
     * Returns the number of available values
     * @return The number of available values
     */
    long getN();
    /**
     * Returns the sum of the values that have been added to Univariate.
     * @return The sum or Double.NaN if no values have been added
     */
    double getSum();

}