v0.0.482 mathext.Percentile

mathext/statistics.go

@@ -1,6 +1,9 @@
 package mathext
 
-import "gogs.mikescher.com/BlackForestBytes/goext/langext"
+import (
+	"gogs.mikescher.com/BlackForestBytes/goext/exerr"
+	"gogs.mikescher.com/BlackForestBytes/goext/langext"
+)
 
 func Sum[T langext.NumberConstraint](v []T) T {
 	total := T(0)
@@ -41,3 +44,53 @@ func ArrMax[T langext.OrderedConstraint](v []T) T {
 	}
 	return r
 }
+
+func MustPercentile[T langext.NumberConstraint](rawdata []T, percentile float64) T {
+	v, err := Percentile(rawdata, percentile)
+	if err != nil {
+		panic(err)
+	}
+	return v
+}
+
+func Percentile[T langext.NumberConstraint](rawdata []T, percentile float64) (T, error) {
+	v, err := FloatPercentile(rawdata, percentile)
+	if err != nil {
+		return T(0), err
+	}
+	return T(v), nil
+
+}
+
+func FloatPercentile[T langext.NumberConstraint](rawdata []T, percentile float64) (float64, error) {
+	if len(rawdata) == 0 {
+		return 0, exerr.New(exerr.TypeAssert, "no data to calculate percentile").Any("percentile", percentile).Build()
+	}
+
+	if percentile < 0 || percentile > 100 {
+		return 0, exerr.New(exerr.TypeAssert, "percentile out of range").Any("percentile", percentile).Build()
+	}
+
+	data := langext.ArrCopy(rawdata)
+	langext.Sort(data)
+
+	idxFloat := float64(len(data)-1) * (percentile / float64(100))
+
+	idxInt := int(idxFloat)
+
+	// exact match on index
+	if idxFloat == float64(idxInt) {
+		return float64(data[idxInt]), nil
+	}
+
+	// linear interpolation
+	v1 := data[idxInt]
+	v2 := data[idxInt+1]
+
+	weight := idxFloat - float64(idxInt)
+
+	valFloat := (float64(v1) * (1 - weight)) + (float64(v2) * weight)
+
+	return valFloat, nil
+
+}