--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/stat.c	Wed Jan 22 12:10:17 2014 +0100
@@ -0,0 +1,43 @@
+#include "stat.h"
+
+void stat_zero(struct stat *s)
+{
+	s->samples = 0;
+	s->mean = 0.0;
+	s->slope = 0.0;
+	s->previous = 0.0;
+}
+
+
+void stat_accumulate(struct stat *s, double value)
+{
+	s->samples += 1;
+	
+	if (s->samples > 1)
+		s->slope = (s->slope * (s->samples - 2) + 6 * (value - s->mean) / s->samples) / (s->samples + 1);
+					
+	s->mean = ((s->samples - 1) * s->mean + value) / s->samples;
+	
+	s->previous = value;
+}
+
+
+void rollmean_zero(struct rollmean *s, int wlen)
+{
+	s->wlen = wlen;
+	s->nobs = 0;
+	s->mean = 0.0;
+	s->acc = 0.0;
+	s->prev = 0.0;
+}
+
+
+void rollmean_accumulate(struct rollmean *s, double value)
+{
+	s->acc = s->acc - s->prev + value;
+	if (s->nobs < s->wlen)
+		s->nobs++;
+	else
+		s->prev = s->acc;
+	s->mean = s->acc / s->nobs;
+}