Fix mode calculation

mathigon · Sep 25, 2024 · 2ad1b94 · 2ad1b94
1 parent c9482fb
commit 2ad1b94
Show file tree

Hide file tree

Showing 2 changed files with 20 additions and 12 deletions.
diff --git a/src/statistics.ts b/src/statistics.ts
@@ -49,17 +49,14 @@ export function mode(values: number[]) {
   let result: number|undefined = undefined;
 
   for (const v of values) {
-    if (!counts.has(v)) {
-      counts.set(v, 1);
-    } else {
-      const newCount = counts.get(v)! + 1;
-      counts.set(v, newCount);
-      if (newCount === maxCount) {
-        result = undefined;
-      } else if (newCount > maxCount) {
-        maxCount = newCount;
-        result = v;
-      }
+    if (!counts.has(v)) counts.set(v, 0);
+    const newCount = counts.get(v)! + 1;
+    counts.set(v, newCount);
+    if (newCount === maxCount) {
+      result = undefined;
+    } else if (newCount > maxCount) {
+      maxCount = newCount;
+      result = v;
     }
   }
 

diff --git a/test/statistics-test.ts b/test/statistics-test.ts
@@ -5,9 +5,20 @@
 
 
 import tape from 'tape';
-import {quantile} from '../src';
+import {mode, quantile} from '../src';
 
 
+tape('mode', (test) => {
+  test.equal(mode([]), undefined);
+  test.equal(mode([2]), 2);
+  test.equal(mode([2, 3]), undefined);
+  test.equal(mode([2, 3, 3]), 3);
+  test.equal(mode([2, 2, 3, 3, 4]), undefined);
+  test.equal(mode([2, 2, 2, 3, 3, 4]), 2);
+
+  test.end();
+});
+
 tape('quantile', (test) => {
   test.equal(quantile([], 0.5), 0);