X-Git-Url: https://bilbo.iut-bm.univ-fcomte.fr/and/gitweb/loba.git/blobdiff_plain/825abbb3bde6c35ab1d1cdfba25fba4be5dcea2f..c2e3e8bc788aa97edc116a151feb705cf77fce57:/statistics.h

diff --git a/statistics.h b/statistics.h
index 2978747..7e3fb2e 100644
--- a/statistics.h
+++ b/statistics.h
@@ -1,29 +1,37 @@
 #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 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