feat: change statistics render of metric plot to min/max/median

- #263

internal/util/statistics.go

@@ -4,7 +4,13 @@
 // license that can be found in the LICENSE file.
 package util
 
-import "golang.org/x/exp/constraints"
+import (
+	"fmt"
+	"math"
+	"sort"
+
+	"golang.org/x/exp/constraints"
+)
 
 func Min[T constraints.Ordered](a, b T) T {
 	if a < b {
@@ -19,3 +25,36 @@ func Max[T constraints.Ordered](a, b T) T {
 	}
 	return b
 }
+
+func sortedCopy(input []float64) []float64 {
+	sorted := make([]float64, len(input))
+	copy(sorted, input)
+	sort.Float64s(sorted)
+	return sorted
+}
+
+func Mean(input []float64) (float64, error) {
+	if len(input) == 0 {
+		return math.NaN(), fmt.Errorf("input array is empty: %#v", input)
+	}
+	sum := 0.0
+	for _, n := range input {
+		sum += n
+	}
+	return sum / float64(len(input)), nil
+}
+
+func Median(input []float64) (median float64, err error) {
+	c := sortedCopy(input)
+	// Even numbers: add the two middle numbers, divide by two (use mean function)
+	// Odd numbers: Use the middle number
+	l := len(c)
+	if l == 0 {
+		return math.NaN(), fmt.Errorf("input array is empty: %#v", input)
+	} else if l%2 == 0 {
+		median, _ = Mean(c[l/2-1 : l/2+1])
+	} else {
+		median = c[l/2]
+	}
+	return median, nil
+}