fix: correct sample method logic; add test

Author: exzos28

src/helpers.test.ts

@@ -0,0 +1,59 @@
+import { scale, sample } from './helpers';
+
+describe('scale function', () => {
+  it('should scale the array values between 0 and 1', () => {
+    const inputArray = [1, 2, 3, 4, 5];
+    const scaledArray = scale(inputArray);
+
+    expect(scaledArray).toEqual([0, 0.25, 0.5, 0.75, 1]);
+  });
+
+  it('should handle an empty array', () => {
+    const inputArray: number[] = [];
+    const scaledArray = scale(inputArray);
+
+    expect(scaledArray).toEqual([]);
+  });
+
+  it('should handle an array with one element', () => {
+    const inputArray = [42];
+    const scaledArray = scale(inputArray);
+
+    expect(scaledArray).toEqual([0]);
+  });
+});
+
+describe('sample function', () => {
+  it('should sample the array to the specified size', () => {
+    const inputArray = [1, 2, 3, 4, 5, 6, 7, 8, 9, 10];
+    const newSize = 5;
+    const sampledArray = sample(inputArray, newSize);
+
+    expect(sampledArray.length).toBe(newSize);
+    expect(sampledArray).toEqual([1, 3, 5, 7, 9]);
+  });
+
+  it('should handle an empty array', () => {
+    const inputArray: number[] = [];
+    const newSize = 0;
+    const sampledArray = sample(inputArray, newSize);
+
+    expect(sampledArray).toEqual([]);
+  });
+
+  it('should handle an array with one element', () => {
+    const inputArray = [42];
+    const newSize = 5;
+    const sampledArray = sample(inputArray, newSize);
+
+    expect(sampledArray).toEqual([42, 42, 42, 42, 42]); // The result will be an array with the same element repeated
+  });
+
+  it('should handle newSize greater than the original size', () => {
+    const inputArray = [1, 2, 3];
+    const newSize = 5;
+    const sampledArray = sample(inputArray, newSize);
+
+    expect(sampledArray).toEqual([1, 1, 2, 2, 3]); // The result will include elements from the original array with repetition
+  });
+});

src/helpers.ts

@@ -1,27 +1,33 @@
 export function scale(arr: number[]) {
+  if (arr.length === 0) {
+    return [];
+  }
+
   const min = Math.min(...arr);
   const max = Math.max(...arr);
   const diff = max - min;
 
-  return arr.map((_) => (_ - min) / diff);
+  if (diff === 0) {
+    // If diff is 0, all elements in the array are the same.
+    // To avoid division by zero, return an array of the same length with 0 values.
+    return arr.map(() => 0);
+  }
+
+  return arr.map((value) => (value - min) / diff);
 }
 
 export function sample(arr: number[], newSize: number) {
   const originalSize = arr.length;
-  const ratio = originalSize / newSize;
-  const result = [];
 
-  for (let i = 0; i < newSize; i++) {
-    const startIndex = Math.floor(i * ratio);
-    const endIndex = Math.floor((i + 1) * ratio);
-    let sum = 0;
+  if (newSize === 0) {
+    return [];
+  }
 
-    for (let j = startIndex; j < endIndex; j++) {
-      sum += arr[j]!;
-    }
+  const result: number[] = [];
 
-    const average = sum / (endIndex - startIndex);
-    result.push(average);
+  for (let i = 0; i < newSize; i++) {
+    const index = Math.floor((i / newSize) * originalSize);
+    result.push(arr[index] ?? 0);
   }
 
   return result;