feat: rename xyClosestX to xyFindClosestPoint and only allow sorted a…

…rray

src/index.ts

@@ -59,7 +59,7 @@ export * from './x/utils/getOutputArray';
 
 export * from './xy/xyAlign';
 export * from './xy/xyCheck';
-export * from './xy/xyClosestX';
+export * from './xy/xyFindClosestPoint';
 export * from './xy/xyCovariance';
 export * from './xy/xyCumulativeDistributionStatistics';
 export * from './xy/xyEnsureGrowingX';

src/xy/__tests__/xyFindClosestPoint.test.ts

@@ -0,0 +1,57 @@
+import { xyFindClosestPoint } from '../xyFindClosestPoint';
+
+describe('closestX', () => {
+  it('should yield the correct result with even element array', () => {
+    const x = [-1, 0, 1, 2, 3, 4, 5, 6];
+    const y = [10, 11, 12, 13, 14, 15, 16, 17];
+    expect(xyFindClosestPoint({ x, y }, -2)).toStrictEqual({
+      x: -1,
+      y: 10,
+    });
+    expect(xyFindClosestPoint({ x, y }, 0.6)).toStrictEqual({
+      x: 1,
+      y: 12,
+    });
+    expect(xyFindClosestPoint({ x, y }, 4.3)).toStrictEqual({
+      x: 4,
+      y: 15,
+    });
+    expect(xyFindClosestPoint({ x, y }, 6)).toStrictEqual({
+      x: 6,
+      y: 17,
+    });
+    expect(xyFindClosestPoint({ x, y }, 7)).toStrictEqual({
+      x: 6,
+      y: 17,
+    });
+  });
+
+  it('should yield the correct result with odd element array', () => {
+    const x = [-1, 0, 1, 2, 3, 4, 5, 6, 7];
+    const y = [10, 11, 12, 13, 14, 15, 16, 17, 18];
+    expect(xyFindClosestPoint({ x, y }, -2)).toStrictEqual({
+      x: -1,
+      y: 10,
+    });
+    expect(xyFindClosestPoint({ x, y }, 0.6)).toStrictEqual({
+      x: 1,
+      y: 12,
+    });
+    expect(xyFindClosestPoint({ x, y }, 4.3)).toStrictEqual({
+      x: 4,
+      y: 15,
+    });
+    expect(xyFindClosestPoint({ x, y }, 6)).toStrictEqual({
+      x: 6,
+      y: 17,
+    });
+    expect(xyFindClosestPoint({ x, y }, 7)).toStrictEqual({
+      x: 7,
+      y: 18,
+    });
+    expect(xyFindClosestPoint({ x, y }, 8)).toStrictEqual({
+      x: 7,
+      y: 18,
+    });
+  });
+});

src/xy/xyFindClosestPoint.ts

@@ -0,0 +1,25 @@
+import binarySearch from 'binary-search';
+import { DataXY, PointXY } from 'cheminfo-types';
+
+import { xFindClosestIndex } from '../x/xFindClosestIndex';
+
+/**
+ * Finds the closest point
+ *
+ * @param data - x array should be sorted and ascending
+ * @param target - target to search
+ * @returns - closest point
+ */
+export function xyFindClosestPoint(
+  /** points */
+  data: DataXY,
+  target: number,
+): PointXY {
+  const { x, y } = data;
+
+  const index = xFindClosestIndex(x, target);
+  return {
+    x: x[index],
+    y: y[index],
+  };
+}