#ifndef STATISTICS_H
#define STATISTICS_H
+#include <cmath>
#include <vector>
class statistics {
public:
- statistics();
-
- void reset();
- void push(double value);
-
- size_t get_count();
- double get_sum();
- double get_avg();
- double get_stddev();
+ statistics()
+ : count(0)
+ , sum(0.0)
+ , mean(0.0)
+ , sqdiff_sum(0.0)
+ { }
+
+ void push(double x) {
+ double delta = x - mean;
+ ++count;
+ sum += x;
+ mean = sum / count;
+ sqdiff_sum += delta * (x - mean);
+ }
+
+ unsigned get_count() const { return count; }
+ double get_sum() const { return sum; }
+ double get_mean() const { return mean; }
+ double get_variance() const { return sqdiff_sum / count; }
+ double get_stddev() const { return std::sqrt(get_variance()); }
private:
- bool up2date;
-
- std::vector<double> values;
- double sum;
- double avg;
- double stddev;
-
- void update();
+ int count;
+ double sum; // sum of x_i
+ double mean; // mean of x_i
+ double sqdiff_sum; // sum of (x_i - mean)^2
};
#endif // !STATISTICS_H
