code: package org.omnetpp.scave.writers;
  
  /**
   * Reporting interface for basic univariate statistics.
   *
   * This is a copy of org.apache.commons.math.stat.descriptive.StatisticalSummary.
   *
   * @see IHistogramSummary
   *
   * @author Andras
   */
  public interface IStatisticalSummary {
      /**
       * Returns the <a href="http://www.xycoon.com/arithmetic_mean.htm">
       * arithmetic mean </a> of the available values
       * @return The mean or Double.NaN if no values have been added.
       */
      public abstract 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.
       */
      public abstract 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.
       */
      public abstract double getStandardDeviation();
  
      /**
       * Returns the maximum of the available values
       * @return The max or Double.NaN if no values have been added.
       */
      public abstract double getMax();
  
      /**
      * Returns the minimum of the available values
      * @return The min or Double.NaN if no values have been added.
      */
      public abstract double getMin();
  
      /**
       * Returns the number of available values
       * @return The number of available values
       */
      public abstract 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
       */
      public abstract double getSum();
  
      /**
       * Returns the squared sum of the values that have been added to Univariate.
       * @return The squared sum or Double.NaN if no values have been added
       *
       * Note: this is not part of the Apache interface, but necessary if one
       * wants to completely restore the statistics calculation object.
       */
      public abstract double getSqrSum();
  }
  