kmeans?

kmeans.js

function kmeans(k, arr) {
	var clusters = [];
	var sorted = [...new Set(arr)].sort((a, b) => a - b);
	var size = Math.abs(sorted.length/k);
	for (var i = 0; sorted.length>0; i += size) {
		if (sorted.length < size*2) size = size*2;
		clusters.push(sorted.splice(0, size));
	}
	console.log(clusters.map((a) => JSON.stringify(a.sort((a, b) => a - b))));
	var center = (a) => {
		var mean = a.reduce((a, v) => a + v, 0)/a.length;
		var closest = 0;
		var dist = Infinity;
		for (let n of a) {
			let d = Math.abs(n-mean);
			if (dist > d) {
				closest = n;
				dist = d;
			}
		}
		return closest;
	};
	var maxdist = (arr) => {
		var c = center(arr);
		return arr.reduce((a, v) => (Math.abs(c-v) > a) ? v : a);
	}
	var variance = (...arrs) => {
		var v = 0;
		var t = 0;
		for (let arr of arrs) {
			var c = center(arr);
			for (let n of arr) {
				t++;
				v += Math.abs(c-n);
			}
		} return v/t;
	}
	console.log('start', variance(...clusters), clusters.map(maxdist));
	var m = Math.max(...clusters.map(maxdist));
	var count = 100, maxiter = 50000;
	while (count>0 && maxiter>0) {
		for (let i in clusters) {
			let c = clusters[i];
			for (let j of [0, c.length-1]) {
				let n = c[j];
				let dist = Math.abs(center(c)-n);
				let back = clusters[parseInt(i)-1],
				    next = clusters[parseInt(i)+1];
				for (let r of [back, next]) {
					if (!r) continue;
					if (Math.abs(center(r)-n) < dist) {
						r.push(...c.splice(j, 1));
					}
				}
			}
			let nvar = Math.max(...clusters.map(maxdist));
			if (nvar < m) m = nvar;
			else count--;
			maxiter--;
		}
	}
	console.log('end', variance(...clusters), clusters.map(maxdist));
	console.log(clusters.map((a) => JSON.stringify(a.sort((a, b) => a - b))));
	return clusters;
}