diff --git a/.travis.yml b/.travis.yml
deleted file mode 100644
index 090a868..0000000
--- a/.travis.yml
+++ /dev/null
@@ -1,11 +0,0 @@
-sudo: false
-language: go
-go:
-- 1.8.x
-- 1.9.x
-- 1.10.x
-- tip
-
-notifications:
-  email:
-    - infra@sajari.com
diff --git a/go.mod b/go.mod
new file mode 100644
index 0000000..d4f0d63
--- /dev/null
+++ b/go.mod
@@ -0,0 +1,5 @@
+module github.com/lamrongol/regression
+
+go 1.24.1
+
+require gonum.org/v1/gonum v0.16.0
diff --git a/go.sum b/go.sum
new file mode 100644
index 0000000..83477d1
--- /dev/null
+++ b/go.sum
@@ -0,0 +1,2 @@
+gonum.org/v1/gonum v0.16.0 h1:5+ul4Swaf3ESvrOnidPp4GZbzf0mxVQpDCYUQE7OJfk=
+gonum.org/v1/gonum v0.16.0/go.mod h1:fef3am4MQ93R2HHpKnLk4/Tbh/s0+wqD5nfa6Pnwy4E=
diff --git a/regression.go b/regression.go
index d5f76fb..5bc62ca 100644
--- a/regression.go
+++ b/regression.go
@@ -31,6 +31,7 @@ type Regression struct {
 	Formula           string
 	crosses           []featureCross
 	hasRun            bool
+	residual_sum_of_squares float64
 }
 
 type dataPoint struct {
@@ -233,15 +234,21 @@ func (r *Regression) calcPredicted() string {
 	observations := len(r.data)
 	var predicted float64
 	var output string
+	r.residual_sum_of_squares = 0.0
 	for i := 0; i < observations; i++ {
 		r.data[i].Predicted, _ = r.Predict(r.data[i].Variables)
 		r.data[i].Error = r.data[i].Predicted - r.data[i].Observed
+		r.residual_sum_of_squares += r.data[i].Error * r.data[i].Error
 
 		output += fmt.Sprintf("%v. observed = %v, Predicted = %v, Error = %v", i, r.data[i].Observed, predicted, r.data[i].Error)
 	}
 	return output
 }
 
+func (r *Regression) GetResidualSumOfSquares() float64 {
+	return r.residual_sum_of_squares
+}
+
 func (r *Regression) calcVariance() string {
 	observations := len(r.data)
 	var obtotal, prtotal, obvar, prvar float64