Adding Mean and MeanBy (#414)

* feat: create Mean for ints and floats

* feat: create MeanBy for ints and floats

* chore: add example tests for mean Mean and MeanBy

math.go

@@ -82,3 +82,23 @@ func SumBy[T any, R constraints.Float | constraints.Integer | constraints.Comple
 	}
 	return sum
 }
+
+// Mean calculates the mean of a collection of numbers.
+func Mean[T constraints.Float | constraints.Integer](collection []T) T {
+	var length T = T(len(collection))
+	if length == 0 {
+		return 0
+	}
+	var sum T = Sum(collection)
+	return sum / length
+}
+
+// MeanBy calculates the mean of a collection of numbers using the given return value from the iteration function.
+func MeanBy[T any, R constraints.Float | constraints.Integer](collection []T, iteratee func(item T) R) R {
+	var length R = R(len(collection))
+	if length == 0 {
+		return 0
+	}
+	var sum R = SumBy(collection, iteratee)
+	return sum / length
+}

math_example_test.go

@@ -66,3 +66,21 @@ func ExampleSumBy() {
 	fmt.Printf("%v", result)
 	// Output: 6
 }
+
+func ExampleMean() {
+	list := []int{1, 2, 3, 4, 5}
+
+	result := Mean(list)
+
+	fmt.Printf("%v", result)
+}
+
+func ExampleMeanBy() {
+	list := []string{"foo", "bar"}
+
+	result := MeanBy(list, func(item string) int {
+		return len(item)
+	})
+
+	fmt.Printf("%v", result)
+}

math_test.go

@@ -97,3 +97,33 @@ func TestSumBy(t *testing.T) {
 	is.Equal(result4, uint32(0))
 	is.Equal(result5, complex128(6_6))
 }
+
+func TestMean(t *testing.T) {
+	t.Parallel()
+	is := assert.New(t)
+
+	result1 := Mean([]float32{2.3, 3.3, 4, 5.3})
+	result2 := Mean([]int32{2, 3, 4, 5})
+	result3 := Mean([]uint32{2, 3, 4, 5})
+	result4 := Mean([]uint32{})
+
+	is.Equal(result1, float32(3.7250001))
+	is.Equal(result2, int32(3))
+	is.Equal(result3, uint32(3))
+	is.Equal(result4, uint32(0))
+}
+
+func TestMeanBy(t *testing.T) {
+	t.Parallel()
+	is := assert.New(t)
+
+	result1 := MeanBy([]float32{2.3, 3.3, 4, 5.3}, func(n float32) float32 { return n })
+	result2 := MeanBy([]int32{2, 3, 4, 5}, func(n int32) int32 { return n })
+	result3 := MeanBy([]uint32{2, 3, 4, 5}, func(n uint32) uint32 { return n })
+	result4 := MeanBy([]uint32{}, func(n uint32) uint32 { return n })
+
+	is.Equal(result1, float32(3.7250001))
+	is.Equal(result2, int32(3))
+	is.Equal(result3, uint32(3))
+	is.Equal(result4, uint32(0))
+}