added new math-stats

started working on a new grid walker

math/stats/Variance.h

@@ -0,0 +1,48 @@
+#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