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/*******************************************************************
 *	STATS.C: Statistics routines:
 *
 *	newsample(n):	Add a new sample to the mean/average totals.
 *	mean():	        Returns the mean of the samples.
 *	deviation():	Returns the standard deviation of the sample.
 *
 ********************************************************************/

#include "apr_stats.h"
#include <cmath>

namespace SEAMS {
  void Stats::newsample(int n)
  {
    double TMean;

    // See Knuth, TAOCP vol 2, 3rd edition, page 232
    TMean = Mean;
    Numnums++;
    Mean = TMean + (n - TMean) / Numnums;

    if (Numnums > 1) {
      StdDev += (n - TMean) * (n - Mean);
    }
  }

  double Stats::mean() const { return Mean; }

  double Stats::variance() const { return (Numnums > 1) ? StdDev / (Numnums - 1) : 0.0; }

  double Stats::deviation() const { return std::sqrt(variance()); }
} // namespace SEAMS
