diff --git a/hw2/graph.py b/hw2/graph.py
new file mode 100644
index 0000000..e2b472d
--- /dev/null
+++ b/hw2/graph.py
@@ -0,0 +1,22 @@
+import numpy as np
+import pandas as pd
+import matplotlib.pyplot as plt
+
+test_data = open("time.txt", "r")
+lines = test_data.readlines()
+time = []
+n = []
+for line in lines:
+    line = line.strip('\n ] [ ').split(' ')
+    time.append(int(line[1]))
+    n.append(int(line[0]))
+test_data.close()
+time.sort()
+n.sort()
+x = n[:-1]
+y = time[:-1]
+plt.plot(x, y, label="the relationship between N and the execution time")
+plt.legend()
+plt.xlabel("N")
+plt.ylabel("time")
+plt.savefig('time.png')
diff --git a/hw2/matrix.go b/hw2/matrix.go
index 058c603..17eac2c 100644
--- a/hw2/matrix.go
+++ b/hw2/matrix.go
@@ -16,6 +16,12 @@ func newMatrix(n int) [][]int {
 	return m
 }
 
+func failOnError(err error) {
+	if err != nil {
+		log.Fatal("Error:", err)
+	}
+}
+
 func main() {
 	if len(os.Args) < 2 {
 		fmt.Println("usage: go run matrix.go N")
@@ -85,4 +91,18 @@ func main() {
 	if want != 0 && total != want {
 		fmt.Printf("Wanted sum %v but got %v\n", want, total)
 	}
+
+	var n_str string
+	var time_str string
+	n_str = strconv.Itoa(n)
+	time_str = strconv.Itoa(int(end.Sub(begin)))
+
+	file, err := os.OpenFile("time.txt", os.O_WRONLY|os.O_APPEND, 0600)
+	if err != nil {
+		log.Fatal(err)
+	}
+	defer file.Close()
+
+	fmt.Fprintln(file, []string{n_str, time_str})
+
 }
diff --git a/hw2/time.png b/hw2/time.png
new file mode 100644
index 0000000..bf98621
Binary files /dev/null and b/hw2/time.png differ
diff --git a/hw2/time.txt b/hw2/time.txt
new file mode 100644
index 0000000..60a7edd
--- /dev/null
+++ b/hw2/time.txt
@@ -0,0 +1,22 @@
+[1 276]
+[2 334]
+[3 537]
+[4 473]
+[5 633]
+[6 861]
+[7 1207]
+[8 1701]
+[9 2318]
+[10 4244]
+[50 351532]
+[100 3060330]
+[200 27809659]
+[300 122514780]
+[400 302434663]
+[400 280376609]
+[500 621763472]
+[600 1039208850]
+[700 2155400336]
+[800 2794530550]
+[900 11907044262]
+[1000 15037068087]