diff --git a/static_src/shared/math.js b/static_src/shared/math.js
new file mode 100644
index 0000000..36e2d75
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+++ b/static_src/shared/math.js
@@ -0,0 +1,26 @@
+// Copyright 2019 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+// Get parameter of generated line using linear regression formula,
+// using last n data points of values.
+export function linearRegression(values, n) {
+  let sumValues = 0;
+  let indices = 0;
+  let sqIndices = 0;
+  let multiply = 0;
+  let temp;
+  for (let i = 0; i < n; i++) {
+    temp = values[values.length-n+i];
+    sumValues += temp;
+    indices += i;
+    sqIndices += i * i;
+    multiply += i * temp;
+  }
+  // Calculate linear regression formula for values.
+  const slope = (n * multiply - sumValues * indices) /
+    (n * sqIndices - indices * indices);
+  const intercept = (sumValues * sqIndices - indices * multiply) /
+    (n * sqIndices - indices * indices);
+  return [slope, intercept];
+}