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// Copyright (C) 1999  Allen Akin   All Rights Reserved.
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// basic.cpp:  basic statistics utilities for glean

#include <cfloat>
#include <cmath>
#include "stats.h"

namespace GLEAN {

void
BasicStats::init() {
	_min = DBL_MAX;
	_max = -DBL_MAX;
	_sum = _sum2 = 0.0;
	_n = 0;
}

double
BasicStats::mean() const {return _n? (_sum / _n): 0.0;}

double
BasicStats::variance() const {
	if (_n < 2)
		return 0.0;
	return (_sum2 - _sum * _sum / _n) / (_n - 1);
		// Not really numerically robust, but good enough for us.
}
double
BasicStats::deviation() const {
	const double v = variance();
	return (v < 0.0)? 0.0: sqrt(v);
}

} // namespace GLEAN