Merge pull request #27 from kevinrobinson/readme-constraints

Add helpful error explanation when size of data doesn't match nNeighbors

Author: cannoneyed

src/umap.ts

@@ -322,6 +322,10 @@ export class UMAP {
    * SGD optimization.
    */
   initializeFit(X: Vectors): number {
+    if (X.length <= this.nNeighbors) {
+      throw new Error(`Not enough data points (${X.length}) to create nNeighbors: ${this.nNeighbors}.  Add more data points or adjust the configuration.`);
+    }
+
     // We don't need to reinitialize if we've already initialized for this data.
     if (this.X === X && this.isInitialized) {
       return this.getNEpochs();

test/umap.test.ts

@@ -202,6 +202,12 @@ describe('UMAP', () => {
 
     expect(nInvocations).toBeGreaterThan(0);
   });
+
+  test('initializeFit throws helpful error if not enough data', () => {
+    const umap = new UMAP({ random });
+    const smallData = testData.slice(0, 15);
+    expect(() => umap.initializeFit(smallData)).toThrow(/Not enough data points/);
+  })
 });
 
 function computeMeanDistances(vectors: number[][]) {