From 7a2ce4b914e057d3827adec74a6cf59024b2f7d9 Mon Sep 17 00:00:00 2001
From: RealPeha <real.peha@gmail.com>
Date: Mon, 5 Oct 2020 14:48:26 +0300
Subject: [PATCH 1/2] Added Mean Square Error

---
 Maths/MeanSquareError.js | 23 +++++++++++++++++++++++
 1 file changed, 23 insertions(+)
 create mode 100644 Maths/MeanSquareError.js

diff --git a/Maths/MeanSquareError.js b/Maths/MeanSquareError.js
new file mode 100644
index 0000000000..1f45ebabfe
--- /dev/null
+++ b/Maths/MeanSquareError.js
@@ -0,0 +1,23 @@
+// Wikipedia: https://en.wikipedia.org/wiki/Mean_squared_error
+
+function mse (predicted, expected) {
+  if (!Array.isArray(predicted) || !Array.isArray(expected)) {
+    throw new TypeError('Argument must be an Array')
+  }
+
+  if (predicted.length !== expected.length) {
+    throw new TypeError('The two lists must be of equal length')
+  }
+
+  let err = 0
+
+  for (let i = 0; i < expected.length; i++) {
+    err += (expected[i] - predicted[i]) ** 2
+  }
+
+  return err / expected.length
+}
+
+console.log(mse([1, 2, 3, 4], [1, 2, 3, 4]) === 0)
+console.log(mse([4, 3, 2, 1], [1, 2, 3, 4]) === 5)
+console.log(mse([2, 0, 2, 0], [0, 0, 0, 0]) === 2)

From 1f74b1fa6e14a34a9c9c34ea19917649d3fac099 Mon Sep 17 00:00:00 2001
From: vinayak <itssvinayak@gmail.com>
Date: Mon, 5 Oct 2020 23:48:00 +0530
Subject: [PATCH 2/2] Update MeanSquareError.js

---
 Maths/MeanSquareError.js | 11 +++++++----
 1 file changed, 7 insertions(+), 4 deletions(-)

diff --git a/Maths/MeanSquareError.js b/Maths/MeanSquareError.js
index 1f45ebabfe..de9dcfd7f0 100644
--- a/Maths/MeanSquareError.js
+++ b/Maths/MeanSquareError.js
@@ -1,6 +1,6 @@
 // Wikipedia: https://en.wikipedia.org/wiki/Mean_squared_error
 
-function mse (predicted, expected) {
+const meanSquaredError = (predicted, expected) => {
   if (!Array.isArray(predicted) || !Array.isArray(expected)) {
     throw new TypeError('Argument must be an Array')
   }
@@ -18,6 +18,9 @@ function mse (predicted, expected) {
   return err / expected.length
 }
 
-console.log(mse([1, 2, 3, 4], [1, 2, 3, 4]) === 0)
-console.log(mse([4, 3, 2, 1], [1, 2, 3, 4]) === 5)
-console.log(mse([2, 0, 2, 0], [0, 0, 0, 0]) === 2)
+// testing
+(() => {
+  console.log(meanSquaredError([1, 2, 3, 4], [1, 2, 3, 4]) === 0)
+  console.log(meanSquaredError([4, 3, 2, 1], [1, 2, 3, 4]) === 5)
+  console.log(meanSquaredError([2, 0, 2, 0], [0, 0, 0, 0]) === 3)
+})()