Adding set.overlap

set.d.ts

@@ -15,3 +15,4 @@ export function disjunct<T>(a: Set<T>, b: Set<T>): void;
 export function intersectionSize<T>(a: Set<T>, b:Set<T>): number;
 export function unionSize<T>(a: Set<T>, b:Set<T>): number;
 export function jaccard<T>(a: Set<T>, b:Set<T>): number;
+export function overlap<T>(a: Set<T>, b: Set<T>): number;

set.js

@@ -277,6 +277,7 @@ exports.disjunct = function(A, B) {
  *
  * @param  {Set} A - First set.
  * @param  {Set} B - Second set.
+ * @return {number}
  */
 exports.intersectionSize = function(A, B) {
   var tmp;
@@ -312,6 +313,7 @@ exports.intersectionSize = function(A, B) {
  *
  * @param  {Set} A - First set.
  * @param  {Set} B - Second set.
+ * @return {number}
  */
 exports.unionSize = function(A, B) {
   var I = exports.intersectionSize(A, B);
@@ -324,6 +326,7 @@ exports.unionSize = function(A, B) {
  *
  * @param  {Set} A - First set.
  * @param  {Set} B - Second set.
+ * @return {number}
  */
 exports.jaccard = function(A, B) {
   var I = exports.intersectionSize(A, B);
@@ -335,3 +338,19 @@ exports.jaccard = function(A, B) {
 
   return I / U;
 };
+
+/**
+ * Function returning the overlap coefficient between A & B.
+ *
+ * @param  {Set} A - First set.
+ * @param  {Set} B - Second set.
+ * @return {number}
+ */
+exports.overlap = function(A, B) {
+  var I = exports.intersectionSize(A, B);
+
+  if (I === 0)
+    return 0;
+
+  return I / Math.min(A.size, B.size);
+};

test/set.js

@@ -177,4 +177,18 @@ describe('Set functions', function() {
       assert.strictEqual(functions.jaccard(new Set('contact'), new Set('context')), 4 / 7);
     });
   });
+
+  describe('#.overlap', function() {
+    it('should properly return the overlap coefficient between two sets.', function() {
+      var A = new Set([1, 2, 3]),
+          B = new Set([2, 3, 4]);
+
+      var N = new Set([]);
+
+      assert.strictEqual(functions.overlap(A, B), 2 / 3);
+      assert.strictEqual(functions.overlap(A, N), 0);
+
+      assert.strictEqual(functions.overlap(new Set('contact'), new Set('context')), 4 / 5);
+    });
+  });
 });