From d4a9eecead23cc66ee8fe8bce37783c9e3c85c3f Mon Sep 17 00:00:00 2001
From: Lazaros Psarokostas <lazarospsa@hotmail.com>
Date: Mon, 18 Dec 2023 20:06:28 +0200
Subject: [PATCH] AverageReturn #12,  AverageReturnAnnualized #13

---
 gofin.go      | 33 +++++++++++++++++++++++++++++++++
 gofin_test.go | 27 +++++++++++++++++++++++++++
 2 files changed, 60 insertions(+)

diff --git a/gofin.go b/gofin.go
index b099beb..5c36aca 100644
--- a/gofin.go
+++ b/gofin.go
@@ -83,6 +83,39 @@ func HoldingPeriodReturnPercentage(initialValue, finalValue float64) float64 {
 	return ((finalValue - initialValue) / initialValue)*100
 }
 
+// AverageReturn calculates the average return over multiple holding periods
+func AverageReturn(holdingPeriodReturns []float64) float64 {
+	totalReturns := 0.0
+	numReturns := len(holdingPeriodReturns)
+
+	if numReturns == 0 {
+		return 0.0 // Avoid division by zero
+	}
+
+	for _, hpr := range holdingPeriodReturns {
+		totalReturns += hpr
+	}
+
+	return totalReturns / float64(numReturns)
+}
+
+// AverageReturnAnnualized calculates the average annualized return over multiple holding periods
+func AverageReturnAnnualized(initialValues, finalValues []float64, holdingPeriods []float64) float64 {
+	totalAnnualizedReturns := 0.0
+	numReturns := len(initialValues)
+
+	if numReturns == 0 {
+		return 0.0 // Avoid division by zero
+	}
+
+	for i := 0; i < numReturns; i++ {
+		annualizedReturn := HoldingPeriodReturnAnnualized(initialValues[i], finalValues[i], holdingPeriods[i])
+		totalAnnualizedReturns += annualizedReturn
+	}
+
+	return totalAnnualizedReturns / float64(numReturns)
+}
+
 // HoldingPeriodReturnAnnualized calculates the annualized holding period return (HPR)
 func HoldingPeriodReturnAnnualized(initialValue, finalValue float64, holdingPeriodInYears float64) float64 {
 	hpr := HoldingPeriodReturn(initialValue, finalValue)
diff --git a/gofin_test.go b/gofin_test.go
index 5278649..9e77e71 100644
--- a/gofin_test.go
+++ b/gofin_test.go
@@ -101,6 +101,33 @@ func TestHoldingPeriodReturnAnnualized(t *testing.T) {
 	}
 }
 
+//test AverageReturnAnnualized
+func TestAverageReturnAnnualized(t *testing.T) {
+	var initialValues []float64 = []float64{1000.0, 1000.0}
+	var finalValues []float64 = []float64{1200.0, 1200.0}
+	var holdingPeriods []float64 = []float64{2.0, 2.0}
+	var expected float64 = 0.10
+
+	actual := AverageReturnAnnualized(initialValues, finalValues, holdingPeriods)
+
+	if compareFloat64(actual, expected) {
+		t.Errorf("Test failed, expected: '%f', got: '%f'", expected, actual)
+	}
+
+}
+
+func TestAverageReturn(t *testing.T) {
+	var holdingPeriodReturns []float64 = []float64{0.10, 0.20}
+	var expected float64 = 0.15
+
+	actual := AverageReturn(holdingPeriodReturns)
+
+	if compareFloat64(actual, expected) {
+		t.Errorf("Test failed, expected: '%f', got: '%f'", expected, actual)
+	}
+
+}
+
 func TestHoldingPeriodReturnAnnualizePercentage(t *testing.T) {
 	var initialValue float64 = 1000.0
 	var finalValue float64 = 1200.0