stats: Add a way to retrieve the standard deviation

Signed-off-by: Damien Lespiau <damien.lespiau@intel.com>

1 files changed, 9 insertions, 0 deletions

diff --git a/lib/igt_stats.c b/lib/igt_stats.c
index 20db806d..65c0ac62 100644
--- a/lib/igt_stats.c
+++ b/lib/igt_stats.c
@@ -22,6 +22,8 @@
  *
  */
 
+#include <math.h>
+
 #include "igt_core.h"
 #include "igt_stats.h"
 
@@ -86,3 +88,10 @@ double igt_stats_get_variance(igt_stats_t *stats)
 
 	return stats->variance;
 }
+
+double igt_stats_get_std_deviation(igt_stats_t *stats)
+{
+	igt_stats_knuth_mean_variance(stats);
+
+	return sqrt(stats->variance);
+}