From e2799cb092359038374cde25eb691d667b309383 Mon Sep 17 00:00:00 2001
From: sanine <sanine.not@pm.me>
Date: Wed, 25 May 2022 22:22:41 -0500
Subject: add Util.js
---
modules/Util.js | 13 +++++++++++++
modules/Util.test.js | 23 +++++++++++++++++++++++
2 files changed, 36 insertions(+)
create mode 100644 modules/Util.js
create mode 100644 modules/Util.test.js
diff --git a/modules/Util.js b/modules/Util.js
new file mode 100644
index 0000000..cbe466d
--- /dev/null
+++ b/modules/Util.js
@@ -0,0 +1,13 @@
+function useAverage() {
+ var avg = 0;
+ let weight = 0;
+ const append = value => {
+ avg = (weight * avg) + value;
+ weight += 1;
+ avg = avg/weight;
+ }
+
+ return [() => avg, append];
+}
+
+export { useAverage };
diff --git a/modules/Util.test.js b/modules/Util.test.js
new file mode 100644
index 0000000..000d54e
--- /dev/null
+++ b/modules/Util.test.js
@@ -0,0 +1,23 @@
+import { test, assert} from './test-assert.js';
+import { useAverage } from './Util.js';
+
+
+test('Average correctly accumulates an average', () => {
+ let [avg, avg_append] = useAverage();
+ let data = [];
+ for (let i=0; i<5000; i++) {
+ let d = Math.random();
+ data.push(d);
+ avg_append(d);
+ }
+
+ let manual_average = 0;
+ for (let d of data) manual_average += d;
+ manual_average /= data.length;
+
+ const precision = (decimalPlaces, num) => {
+ const theta = 10**decimalPlaces;
+ return Math.floor(num * theta) / theta;
+ };
+ assert.equal(precision(5, avg()), precision(5, manual_average));
+});
--
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