Initial commit

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

common/maths/mode.go

@@ -0,0 +1,41 @@
+package maths
+
+func Mode(input Float64Data) (mode []float64, err error) {
+	l := input.Len()
+	if l == 1 {
+		return input, nil
+	}
+	if l == 0 {
+		return nil, EmptyInputErr
+	}
+	c := sortedCopyDif(input)
+	// Traverse sorted array,
+	// tracking the longest repeating sequence
+	mode = make([]float64, 5)
+	cnt, maxCnt := 1, 1
+	for i := 1; i < l; i++ {
+		switch {
+		case c[i] == c[i-1]:
+			cnt++
+		case cnt == maxCnt && maxCnt != 1:
+			mode = append(mode, c[i-1])
+			cnt = 1
+		case cnt > maxCnt:
+			mode = append(mode[:0], c[i-1])
+			maxCnt, cnt = cnt, 1
+		default:
+			cnt = 1
+		}
+	}
+	switch {
+	case cnt == maxCnt:
+		mode = append(mode, c[l-1])
+	case cnt > maxCnt:
+		mode = append(mode[:0], c[l-1])
+		maxCnt = cnt
+	}
+	if maxCnt == 1 || len(mode)*maxCnt == l && maxCnt != l {
+		return Float64Data{}, nil
+	}
+	return mode, nil
+}