feat: add regression lines and dataset transform bin

packages/vdataset/__tests__/bin.test.ts

@@ -0,0 +1,62 @@
+import bin from '../src/transform/bin';
+
+describe('bin transform', () => {
+  test('basic bins by count', () => {
+    const data = [] as any[];
+    for (let i = 0; i < 100; i++) {
+      data.push({ v: i });
+    }
+    const bins = bin(data, { field: 'v', bins: 10 });
+    expect(bins.length).toBe(10);
+    const total = bins.reduce((s: number, b: any) => s + b.count, 0);
+    expect(total).toBe(100);
+    // each bin should have roughly 10 counts
+    for (let i = 0; i < bins.length; i++) {
+      expect(bins[i].count).toBeGreaterThanOrEqual(8);
+      expect(bins[i].count).toBeLessThanOrEqual(12);
+    }
+  });
+
+  test('step produces correct bin widths', () => {
+    const data = [] as any[];
+    for (let i = 0; i <= 20; i++) {
+      data.push({ v: i });
+    }
+    const bins = bin(data, { field: 'v', step: 5 });
+    // step=5 -> bins covering [min,max] with width 5 => expect 5 bins (0-4,5-9,10-14,15-19,20)
+    expect(bins.length).toBeGreaterThanOrEqual(4);
+    // ensure bin edges spacing equals 5 or last smaller
+    for (let i = 0; i < bins.length - 1; i++) {
+      const w = bins[i].x1 - bins[i].x0;
+      expect(w).toBeCloseTo(5, 12);
+    }
+  });
+
+  test('explicit thresholds control bin edges', () => {
+    const data = [{ v: 1 }, { v: 3 }, { v: 7 }, { v: 12 }];
+    const thresholds = [0, 5, 10, 20];
+    const bins = bin(data, { field: 'v', thresholds });
+    expect(bins.length).toBe(3);
+    expect(bins[0].count).toBe(2); // 1 and 3
+    expect(bins[1].count).toBe(1); // 7
+    expect(bins[2].count).toBe(1); // 12
+  });
+
+  test('extent overrides and includeValues', () => {
+    const data = [
+      { v: 2, id: 'a' },
+      { v: 8, id: 'b' }
+    ];
+    const bins = bin(data, { field: 'v', step: 5, extent: [0, 10], includeValues: true });
+    expect(bins.length).toBeGreaterThan(0);
+    const values = bins.flatMap((b: any) => (b.values ? b.values.map((it: any) => it.id) : []));
+    expect(values).toContain('a');
+    expect(values).toContain('b');
+  });
+
+  test('empty data returns empty array', () => {
+    const out = bin([], { field: 'x', bins: 5 });
+    expect(Array.isArray(out)).toBeTruthy();
+    expect(out.length).toBe(0);
+  });
+});

packages/vdataset/src/index.ts

@@ -17,6 +17,8 @@ export type { IMapOptions } from './transform/map';
 export { fold } from './transform/fold';
 export type { IFoldOptions } from './transform/fold';
 export { fields } from './transform/fields';
+export type { IBinOptions } from './transform/bin';
+export { bin } from './transform/bin';
 export type { IFieldsOptions } from './transform/fields';
 // transformType
 export * from './transform/index';

packages/vdataset/src/transform/bin.ts

@@ -0,0 +1,125 @@
+import { isNil } from '@visactor/vutils';
+import type { Transform } from '.';
+
+export interface IBinOptions {
+  field: string; // numeric field to bin
+  bins?: number; // number of bins (default 10)
+  thresholds?: number[]; // explicit bin edges
+  step?: number; // optional fixed bin width (interval step). If provided, overrides bins.
+  extent?: [number, number]; // optional [min, max] to use instead of data-driven
+  includeValues?: boolean; // whether to keep the original items in each bin
+}
+
+/**
+ * Bin transform: converts numeric field into histogram bins.
+ * Returns an array of bins: { x0, x1, count, values? }
+ */
+export const bin: Transform = (data: Array<object>, options?: IBinOptions) => {
+  const field = options?.field;
+  if (!field) {
+    return [];
+  }
+
+  const n = data.length;
+  // compute data-driven extent
+  let min = Infinity;
+  let max = -Infinity;
+
+  if (options?.extent) {
+    min = options.extent[0];
+    max = options.extent[1];
+  } else {
+    for (let i = 0; i < n; i++) {
+      const v: any = (data[i] as any)[field];
+      if (isNil(v)) {
+        continue;
+      }
+      const num = +v;
+      if (Number.isFinite(num)) {
+        if (num < min) {
+          min = num;
+        }
+        if (num > max) {
+          max = num;
+        }
+      }
+    }
+  }
+
+  if (!Number.isFinite(min) || !Number.isFinite(max) || n === 0) {
+    return [];
+  }
+
+  // build thresholds
+  let thresholds: number[] | undefined;
+  if (options && options.thresholds && options.thresholds.length) {
+    // explicit thresholds provided by user
+    thresholds = options.thresholds.slice();
+    thresholds.sort((a, b) => a - b);
+  } else if (options && typeof options.step === 'number' && options.step > 0) {
+    // fixed bin width (step) provided: compute number of bins to cover [min, max]
+    const stepSize = options.step;
+    let startMin = min;
+
+    if (!options.extent) {
+      startMin = Math.floor(min / stepSize) * stepSize;
+    }
+    thresholds = [startMin];
+
+    while (startMin < max) {
+      startMin += stepSize;
+      thresholds.push(startMin);
+    }
+  } else {
+    // fallback to bins count (default 10)
+    const bins = options?.bins && options.bins > 0 ? Math.floor(options.bins) : 10;
+    const stepSize = (max - min) / bins;
+    thresholds = new Array(bins + 1);
+    for (let i = 0; i <= bins; i++) {
+      thresholds[i] = i === bins ? max : min + stepSize * i;
+    }
+  }
+
+  const numBins = Math.max(0, thresholds.length - 1);
+  if (numBins === 0) {
+    return [];
+  }
+
+  const out: any[] = new Array(numBins);
+  for (let i = 0; i < numBins; i++) {
+    out[i] = { x0: thresholds[i], x1: thresholds[i + 1], count: 0 };
+    if (options?.includeValues) {
+      out[i].values = [] as object[];
+    }
+  }
+
+  // assign each datum to a bin (left-inclusive, right-exclusive except last bin includes max)
+  for (let i = 0; i < n; i++) {
+    const v: any = (data[i] as any)[field];
+    if (v == null) {
+      continue;
+    }
+    const num = +v;
+    if (!Number.isFinite(num)) {
+      continue;
+    }
+
+    // find bin index (linear scan is fine for moderate bin counts)
+    for (let j = 0; j < numBins; j++) {
+      const left = out[j].x0;
+      const right = out[j].x1;
+      const isLast = j === numBins - 1;
+      if ((num >= left && num < right) || (isLast && num <= right)) {
+        out[j].count++;
+        if (options && options.includeValues) {
+          out[j].values.push(data[i]);
+        }
+        break;
+      }
+    }
+  }
+
+  return out;
+};
+
+export default bin;

packages/vutils/__tests__/common/regression-linear.test.ts

@@ -12,6 +12,6 @@ test('regressionLinear()', function () {
     }
   ];
   const res = regressionLinear(arr);
-  expect(res.coef).toEqual([0, 2]);
+  expect(res.coef).toEqual({ a: 0, b: 2 });
   expect(res.predict(1)).toBeCloseTo(2);
 });

packages/vutils/__tests__/ecdf.test.ts

@@ -0,0 +1,36 @@
+import ecdf from '../src/common/ecdf';
+
+describe('ecdf', () => {
+  test('evaluate single and array and grid', () => {
+    const data = [1, 2, 2, 3];
+    const e = ecdf(data);
+    expect(e.n).toBe(4);
+    expect(e.evaluate(2)).toBeCloseTo(3 / 4);
+    expect(e.evaluate([0, 2, 4])).toEqual([0, 3 / 4, 1]);
+    const g = e.evaluateGrid(5);
+    expect(g.length).toBe(5);
+    // monotone non-decreasing
+    for (let i = 1; i < g.length; i++) {
+      expect(g[i].y).toBeGreaterThanOrEqual(g[i - 1].y);
+    }
+  });
+
+  test('empty and constant data', () => {
+    const e0 = ecdf([]);
+    expect(e0.n).toBe(0);
+    expect(e0.evaluate(1)).toBe(0);
+    const e1 = ecdf([5, 5, 5]);
+    const g = e1.evaluateGrid(3);
+    expect(g.every(p => p.x === 5)).toBeTruthy();
+    expect(g.every(c => c.y === 1)).toBeTruthy();
+  });
+
+  test('evaluate array and single consistent', () => {
+    const data = [3, 1, 4, 1, 5];
+    const model = ecdf(data);
+    const x = 2;
+    const a = model.evaluate(x) as number;
+    const b = (model.evaluate([x]) as number[])[0];
+    expect(a).toBeCloseTo(b, 12);
+  });
+});

packages/vutils/__tests__/kde.test.ts

@@ -0,0 +1,111 @@
+import { epanechnikov, gaussian, kde, scott, silverman } from '../src/common/kde';
+
+describe('kde', () => {
+  test('evaluate and grid', () => {
+    const data = [1, 2, 3, 4, 5];
+    const model = kde(data, { bandwidthMethod: 'scott' });
+    expect(typeof model.bandwidth).toBe('number');
+    const v = model.evaluate(3);
+    expect(typeof v).toBe('number');
+    const arr = model.evaluate([1, 2, 3]);
+    expect(Array.isArray(arr)).toBeTruthy();
+    const g = model.evaluateGrid(10);
+    expect(Array.isArray(g)).toBeTruthy();
+    expect(g.length).toBe(10);
+  });
+
+  test('constant data returns zeros density when bandwidth is zero', () => {
+    const data = [5, 5, 5];
+    const model = kde(data, { bandwidth: 0 });
+    const g = model.evaluateGrid(3);
+    expect(g.length).toBe(3);
+    expect(g.every(d => d.y === 0)).toBeTruthy();
+  });
+});
+
+describe('kde', () => {
+  test('basic gaussian kde returns higher density near samples (evaluator API)', () => {
+    const data = [0, 0, 1, 2, 3];
+    const points = [-1, 0, 0.5, 1, 2, 4];
+    const model = kde(data, { kernel: gaussian, bandwidth: 0.5 });
+    const densities = model.evaluate(points) as number[];
+    // highest density should be at 0 or 1 (near data points)
+    const maxIdx = densities.indexOf(Math.max(...densities));
+    expect(points[maxIdx]).toBeGreaterThanOrEqual(0);
+    expect(densities.length).toBe(points.length);
+  });
+
+  test('epanechnikov kernel gives finite densities and respects bandwidth selectors (evaluator)', () => {
+    const data = [1, 2, 3, 4, 5];
+    const points = [0, 1, 2, 3, 4, 5, 6];
+    const model1 = kde(data, { kernel: epanechnikov, bandwidthMethod: 'scott' });
+    const model2 = kde(data, { kernel: epanechnikov, bandwidthMethod: 'silverman' });
+    const d1 = model1.evaluate(points) as number[];
+    const d2 = model2.evaluate(points) as number[];
+    expect(d1.length).toBe(points.length);
+    expect(d2.length).toBe(points.length);
+    for (let i = 0; i < d1.length; i++) {
+      expect(isFinite(d1[i])).toBe(true);
+      expect(isFinite(d2[i])).toBe(true);
+    }
+  });
+
+  test('bandwidth helpers roughly scale with n and std', () => {
+    const s = 2;
+    const h1 = scott(100, s);
+    const h2 = silverman(100, s);
+    expect(h1).toBeGreaterThan(0);
+    expect(h2).toBeGreaterThan(0);
+  });
+
+  test('evaluateGrid returns N points and densities', () => {
+    const data = [0, 1, 2];
+    const model = kde(data, { kernel: gaussian, bandwidth: 0.5 });
+    const res = model.evaluateGrid(5);
+    expect(res.length).toBe(5);
+    // points should be in increasing order
+    for (let i = 1; i < res.length; i++) {
+      expect(res[i].x).toBeGreaterThanOrEqual(res[i - 1].x);
+    }
+  });
+
+  test('evaluate(single) equals evaluate([single]) and is finite', () => {
+    const data = [0, 1, 2, 3];
+    const model = kde(data, { kernel: gaussian });
+    const x = 1.3;
+    const a = model.evaluate(x) as number;
+    const b = (model.evaluate([x]) as number[])[0];
+    expect(typeof a).toBe('number');
+    expect(Number.isFinite(a)).toBe(true);
+    expect(a).toBeCloseTo(b, 12);
+  });
+
+  test('constant data evaluateGrid returns repeated point and same densities', () => {
+    const data = [5, 5, 5];
+    const model = kde(data, { kernel: gaussian });
+    const res = model.evaluateGrid(4);
+    expect(res.length).toBe(4);
+    // all points should equal 5 and all densities should be equal
+    for (let i = 0; i < res.length; i++) {
+      expect(res[i].x).toBe(5);
+      expect(res[i].y).toBeCloseTo(res[0].y, 12);
+    }
+  });
+
+  test('kernels produce non-negative finite densities and bandwidth present', () => {
+    const data = [0, 2, 4, 6];
+    const modelG = kde(data, { kernel: gaussian });
+    const modelE = kde(data, { kernel: epanechnikov });
+    const testPoints = [0, 1, 2, 3, 4];
+    const dg = modelG.evaluate(testPoints) as number[];
+    const de = modelE.evaluate(testPoints) as number[];
+    for (let i = 0; i < testPoints.length; i++) {
+      expect(Number.isFinite(dg[i])).toBe(true);
+      expect(dg[i]).toBeGreaterThanOrEqual(0);
+      expect(Number.isFinite(de[i])).toBe(true);
+      expect(de[i]).toBeGreaterThanOrEqual(0);
+    }
+    expect(modelG.bandwidth).toBeGreaterThan(0);
+    expect(modelE.bandwidth).toBeGreaterThan(0);
+  });
+});