jtBaseApp/node_modules/skmeans/dist/node/kinit.js

"use strict";

var Distance = require("./distance.js"),
    eudist = Distance.eudist,
    dist = Distance.dist;

module.exports = {
	kmrand: function kmrand(data, k) {
		var map = {},
		    ks = [],
		    t = k << 2;
		var len = data.length;
		var multi = data[0].length > 0;

		while (ks.length < k && t-- > 0) {
			var d = data[Math.floor(Math.random() * len)];
			var key = multi ? d.join("_") : "" + d;
			if (!map[key]) {
				map[key] = true;
				ks.push(d);
			}
		}

		if (ks.length < k) throw new Error("Error initializating clusters");else return ks;
	},


	/**
  * K-means++ initial centroid selection
  */
	kmpp: function kmpp(data, k) {
		var distance = data[0].length ? eudist : dist;
		var ks = [],
		    len = data.length;
		var multi = data[0].length > 0;
		var map = {};

		// First random centroid
		var c = data[Math.floor(Math.random() * len)];
		var key = multi ? c.join("_") : "" + c;
		ks.push(c);
		map[key] = true;

		// Retrieve next centroids
		while (ks.length < k) {
			// Min Distances between current centroids and data points
			var dists = [],
			    lk = ks.length;
			var dsum = 0,
			    prs = [];

			for (var i = 0; i < len; i++) {
				var min = Infinity;
				for (var j = 0; j < lk; j++) {
					var _dist = distance(data[i], ks[j]);
					if (_dist <= min) min = _dist;
				}
				dists[i] = min;
			}

			// Sum all min distances
			for (var _i = 0; _i < len; _i++) {
				dsum += dists[_i];
			}

			// Probabilities and cummulative prob (cumsum)
			for (var _i2 = 0; _i2 < len; _i2++) {
				prs[_i2] = { i: _i2, v: data[_i2], pr: dists[_i2] / dsum, cs: 0 };
			}

			// Sort Probabilities
			prs.sort(function (a, b) {
				return a.pr - b.pr;
			});

			// Cummulative Probabilities
			prs[0].cs = prs[0].pr;
			for (var _i3 = 1; _i3 < len; _i3++) {
				prs[_i3].cs = prs[_i3 - 1].cs + prs[_i3].pr;
			}

			// Randomize
			var rnd = Math.random();

			// Gets only the items whose cumsum >= rnd
			var idx = 0;
			while (idx < len - 1 && prs[idx++].cs < rnd) {}
			ks.push(prs[idx - 1].v);
			/*
   let done = false;
   while(!done) {
   	// this is our new centroid
   	c = prs[idx-1].v
   	key = multi? c.join("_") : `${c}`;
   	if(!map[key]) {
   		map[key] = true;
   		ks.push(c);
   		done = true;
   	}
   	else {
   		idx++;
   	}
   }
   */
		}

		return ks;
	}
};
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