Fix bug in label encoder transformer

Author: risenW

src/danfojs-base/transformers/encoders/label.encoder.ts

@@ -82,7 +82,8 @@ export default class LabelEncoder {
     transform(data: Array<string | number> | typeof tensorflow.Tensor | Series) {
         const $data = this.$getData(data)
         const encodedData: Array<number> = $data.map(value => {
-            return this.$labels[value]
+            const label = this.$labels[value] !== undefined ? this.$labels[value] : -1
+            return label
         })
 
         if (data instanceof Array) {

src/danfojs-browser/tests/transformers/label.encoder.test.js

@@ -16,6 +16,14 @@ describe("LabelEncoder", function () {
     const expected = [ 0, 1, 1, 2, 3, 3 ];
     assert.deepEqual(scaler.transform(sf), expected);
   });
+  it("LabelEncoder works for values not found", function () {
+    const sf = new dfd.Series([ 1, 2, 2, 6 ]);
+    const scaler = new dfd.LabelEncoder();
+    scaler.fit(sf);
+
+    const expected = [ 0, 1, 1, 2, -1 ];
+    assert.deepEqual((scaler.transform(new Series([ 1, 2, 2, 6, 7 ]))).values, expected);
+  });
   it("fitTransform works for 1D array", function () {
     const sf = [ 1, 2, 2, "boy", "git", "git" ];
     const scaler = new dfd.LabelEncoder();

src/danfojs-node/test/core/daterange.test.ts

@@ -1,4 +1,5 @@
 import { assert } from "chai";
+import { describe, it } from "mocha";
 import { dateRange } from '../../dist/danfojs-node/src';
 
 

src/danfojs-node/test/transformers/label.encoder.test.ts

@@ -11,6 +11,14 @@ describe("LabelEncoder", function () {
         const expected = [0, 1, 1, 2];
         assert.deepEqual((scaler.transform(sf) as Series).values, expected);
     });
+    it("LabelEncoder works for values not found", function () {
+        const sf = new Series([1, 2, 2, 6])
+        const scaler = new LabelEncoder();
+        scaler.fit(sf);
+
+        const expected = [0, 1, 1, 2, -1];
+        assert.deepEqual((scaler.transform(new Series([1, 2, 2, 6, 7])) as Series).values, expected);
+    });
     it("LabelEncoder works for 1D array", function () {
         const sf = [1, 2, 2, "boy", "git", "git"]
         const scaler = new LabelEncoder();