From 9d07492261001aa480901b9928a76db8f22f6b7a Mon Sep 17 00:00:00 2001
From: Chris Bubernak <chris.bubernak@gmail.com>
Date: Tue, 24 Aug 2021 08:38:51 -0700
Subject: [PATCH] Add option to seed the randomness for predictable results

---
 README.md         |  1 +
 lib/kmeans.js     |  5 ++++-
 package-lock.json |  5 +++++
 package.json      |  1 +
 test/index.js     | 12 ++++++++++++
 5 files changed, 23 insertions(+), 1 deletion(-)

diff --git a/README.md b/README.md
index 192721d..5943c4b 100644
--- a/README.md
+++ b/README.md
@@ -38,6 +38,7 @@ kmeans.clusterize(vectors, {k: 4}, (err,res) => {
  - **options** object:
     - **k** : number of clusters
     - **distance** (optional) : custom distance function returning the distance between two points `(a,b) => number`, *default* Euclidian Distance
+    - **seed** (optional) : value that can be provided to get repeatable cluster generation
  - **callback** node-style callback taking error and result argument
 
 ## Outputs
diff --git a/lib/kmeans.js b/lib/kmeans.js
index e93c558..bdce711 100644
--- a/lib/kmeans.js
+++ b/lib/kmeans.js
@@ -18,6 +18,7 @@ The kmeans will return an error if:
   - The number of different input vectors is smaller than k
 */
 
+const seedrandom = require('seedRandom');
 const _ = require('underscore');
 
 
@@ -60,7 +61,8 @@ class Group {
     if (this.centroid && this.cluster.length > 0) {
       this.calculateCentroid();
     } else { // random selection
-      const i = Math.floor(Math.random() * self.indexes.length);
+      const rand = self.seed == null ? Math.random() : seedrandom(self.seed)();
+      const i = Math.floor(rand * self.indexes.length);
       this.centroidIndex = self.indexes[i];
       self.indexes.splice(i, 1);
       this.centroid = [];
@@ -126,6 +128,7 @@ class Clusterize {
     this.options = options;
     this.v = this.checkV(vector);
     this.k = this.options.k;
+    this.seed = this.options.seed;
     this.distanceFunction = this.options.distance || euclidianDistance;
     if (this.v.length < this.k) {
       const errMessage = `The number of points must be greater than
diff --git a/package-lock.json b/package-lock.json
index 649db58..14ed099 100644
--- a/package-lock.json
+++ b/package-lock.json
@@ -1962,6 +1962,11 @@
       "integrity": "sha512-YZo3K82SD7Riyi0E1EQPojLz7kpepnSQI9IyPbHHg1XXXevb5dJI7tpyN2ADxGcQbHG7vcyRHk0cbwqcQriUtg==",
       "dev": true
     },
+    "seedrandom": {
+      "version": "3.0.5",
+      "resolved": "https://registry.npmjs.org/seedrandom/-/seedrandom-3.0.5.tgz",
+      "integrity": "sha512-8OwmbklUNzwezjGInmZ+2clQmExQPvomqjL7LFqOYqtmuxRgQYqOD3mHaU+MvZn5FLUeVxVfQjwLZW/n/JFuqg=="
+    },
     "semver": {
       "version": "5.7.0",
       "resolved": "https://registry.npmjs.org/semver/-/semver-5.7.0.tgz",
diff --git a/package.json b/package.json
index 738c6df..1a72374 100644
--- a/package.json
+++ b/package.json
@@ -12,6 +12,7 @@
     "node": ">= v0.6.0"
   },
   "dependencies": {
+    "seedrandom": "^3.0.5",
     "underscore": "^1.9.1"
   },
   "devDependencies": {
diff --git a/test/index.js b/test/index.js
index 9fde4b2..0f95fb8 100644
--- a/test/index.js
+++ b/test/index.js
@@ -139,5 +139,17 @@ describe('kmeans', () => {
         done();
       });
     });
+
+    it('should produce consistent output when a seed is provided', (done) => {
+      kmeans.clusterize(data3D, { k: 3, seed: 42 }, (err, res) => {
+
+        // Verify first value of each centroid is always the same
+        const cs = res.map(r => r.centroid[0]);
+        cs[0].should.equal(202.6);
+        cs[1].should.equal(-10.15);
+        cs[2].should.equal(39.75);
+        done();
+      });
+    });
   });
 });