Data commit

Task/Cumulative-standard-deviation/C/cumulative-standard-deviation-1.c

@@ -0,0 +1,48 @@
+#include <stdio.h>
+#include <stdlib.h>
+#include <math.h>
+
+typedef enum Action { STDDEV, MEAN, VAR, COUNT } Action;
+
+typedef struct stat_obj_struct {
+   double sum, sum2;
+   size_t num;
+   Action action;
+} sStatObject, *StatObject;
+
+StatObject NewStatObject( Action action )
+{
+  StatObject so;
+
+  so = malloc(sizeof(sStatObject));
+  so->sum = 0.0;
+  so->sum2 = 0.0;
+  so->num = 0;
+  so->action = action;
+  return so;
+}
+#define FREE_STAT_OBJECT(so) \
+   free(so); so = NULL
+double stat_obj_value(StatObject so, Action action)
+{
+  double num, mean, var, stddev;
+
+  if (so->num == 0.0) return 0.0;
+  num = so->num;
+  if (action==COUNT) return num;
+  mean = so->sum/num;
+  if (action==MEAN) return mean;
+  var = so->sum2/num - mean*mean;
+  if (action==VAR) return var;
+  stddev = sqrt(var);
+  if (action==STDDEV) return stddev;
+  return 0;
+}
+
+double stat_object_add(StatObject so, double v)
+{
+  so->num++;
+  so->sum += v;
+  so->sum2 += v*v;
+  return stat_obj_value(so, so->action);
+}

Task/Cumulative-standard-deviation/C/cumulative-standard-deviation-2.c

@@ -0,0 +1,13 @@
+double v[] = { 2,4,4,4,5,5,7,9 };
+
+int main()
+{
+  int i;
+  StatObject so = NewStatObject( STDDEV );
+
+  for(i=0; i < sizeof(v)/sizeof(double) ; i++)
+    printf("val: %lf  std dev: %lf\n", v[i], stat_object_add(so, v[i]));
+
+  FREE_STAT_OBJECT(so);
+  return 0;
+}