add subset algorithm

core/mathx/entropy.go

@@ -2,9 +2,14 @@ package mathx
 
 import "math"
 
-func CalcEntropy(m map[interface{}]int, total int) float64 {
+func CalcEntropy(m map[interface{}]int) float64 {
 	var entropy float64
 
+	var total int
+	for _, v := range m {
+		total += v
+	}
+
 	for _, v := range m {
 		proba := float64(v) / float64(total)
 		entropy -= proba * math.Log2(proba)