silhouette.test.js

/* eslint no-shadow: 0 */

const test = require("tap").test;
const ss = require("../dist/simple-statistics.js");

test("silhouette test", function (t) {
    t.test("Requires equal-sized arrays", function (t) {
        t.throws(function () {
            ss.silhouette([[0]], [1, 2]);
        });
        t.end();
    });

    t.test("Single cluster of one point has metric 0", function (t) {
        const points = [[0.5]];
        const labels = [0];
        const actual = ss.silhouette(points, labels);
        t.same(actual, [0.0]);
        const metric = ss.silhouetteMetric(points, labels);
        t.equal(metric, 0.0);
        t.end();
    });

    t.test("Single cluster of two points has metric 1.0", function (t) {
        const points = [[0.25], [0.75]];
        const labels = [0, 0];
        const actual = ss.silhouette(points, labels);
        t.same(actual, [1.0, 1.0]);
        const metric = ss.silhouetteMetric(points, labels);
        t.equal(metric, 1.0);
        t.end();
    });

    t.test("Two clusters with one point each has metric 0.0", function (t) {
        const points = [[0.25], [0.75]];
        const labels = [0, 1];
        const actual = ss.silhouette(points, labels);
        t.same(actual, [0.0, 0.0]);
        const metric = ss.silhouetteMetric(points, labels);
        t.equal(metric, 0.0);
        t.end();
    });

    // Outer points have a = 0.1, b = 0.5, s = 4/5.
    // Inner points have a = 0.1, b = 0.3, s = 2/3.
    t.test("Two clusters with two points each has metric 0.5", function (t) {
        const points = [[0.2], [0.4], [0.6], [0.8]];
        const labels = [0, 0, 1, 1];
        const actual = ss.silhouette(points, labels);
        const expected = [4 / 5, 2 / 3, 2 / 3, 4 / 5];
        t.ok(actual.every((val, i) => ss.approxEqual(val, expected[i])));
        const metric = ss.silhouetteMetric(points, labels);
        t.ok(ss.approxEqual(metric, 4 / 5));
        t.end();
    });

    t.end();
});