Fix the way in which median is calculated. If the data source has even

number of data points, value should be calculated by adding two middle
elements and dividing them by 2.

Approved by:	cognet (mentor)

2 files changed, 36 insertions, 14 deletions

diff --git a/tools/tools/ministat/ministat.c b/tools/tools/ministat/ministat.c
index 038ef6b..af3f803 100644
--- a/tools/tools/ministat/ministat.c
+++ b/tools/tools/ministat/ministat.c
@@ -202,15 +202,26 @@ Avg(struct dataset *ds)
 static double
 Median(struct dataset *ds)
 {
-	int i;
-	struct point *pp;
+	int even, i;
+	struct point *p1, *p2;
 
-	i = ds->n / 2;
-	TAILQ_FOREACH(pp, &ds->list, list) {
-		if (i--)
-			continue;
-		return (pp->val);
+	if ((ds->n % 2) == 1) {
+		i = (ds->n / 2) + 1;
+		even = 0;
+	} else {
+		i = ds->n / 2;
+		even = 1;
+	}
+	TAILQ_FOREACH(p1, &ds->list, list) {
+		--i;
+		if (i == 0)
+			break;
+	}
+	if (even) {
+		p2 = TAILQ_NEXT(p1, list);
+		return ((p2->val + p1->val) / 2);
 	}
+	return (p1->val);
 }
 
 static double
diff --git a/usr.bin/ministat/ministat.c b/usr.bin/ministat/ministat.c
index 038ef6b..af3f803 100644
--- a/usr.bin/ministat/ministat.c
+++ b/usr.bin/ministat/ministat.c
@@ -202,15 +202,26 @@ Avg(struct dataset *ds)
 static double
 Median(struct dataset *ds)
 {
-	int i;
-	struct point *pp;
+	int even, i;
+	struct point *p1, *p2;
 
-	i = ds->n / 2;
-	TAILQ_FOREACH(pp, &ds->list, list) {
-		if (i--)
-			continue;
-		return (pp->val);
+	if ((ds->n % 2) == 1) {
+		i = (ds->n / 2) + 1;
+		even = 0;
+	} else {
+		i = ds->n / 2;
+		even = 1;
+	}
+	TAILQ_FOREACH(p1, &ds->list, list) {
+		--i;
+		if (i == 0)
+			break;
+	}
+	if (even) {
+		p2 = TAILQ_NEXT(p1, list);
+		return ((p2->val + p1->val) / 2);
 	}
+	return (p1->val);
 }
 
 static double