#ifndef STATS_VARIANCE_H
#define STATS_VARIANCE_H

#include "../../Assertions.h"
#include "Average.h"

namespace Stats {

	template <typename Scalar> class Variance {

		Average<Scalar> avg;
		Average<Scalar> avg2;

	public:

		/** ctor */
		Variance() {
			;
		}

		/** contains valid data? */
		bool isValid() const {
			return avg.isValid();
		}

		/** add a new value */
		void add(const Scalar val) {
			avg.add(val);
			avg2.add(val*val);
		}

		/** get the current variance */
		Scalar get() const {
			Assert::isTrue(avg.isValid(), "add() values first!");
			return avg2.get() - (avg.get()*avg.get());
		}

		/** get the current stadard-deviation */
		Scalar getStdDev() const {
			return std::sqrt(get());
		}


	};

}

#endif // STATS_VARIANCE_H