Linear Regression

regeression.js

//an implementation of the AIClass linear regression algorithm
//http://www.youtube.com/watch?v=CE-R7a5xodI#t=4m18s

var x = [1,2,3,4], y = [2,3,4,5]; 
var M = x.length;

function sumxy(fn){
	var sum = 0;
	for(var i = 0; i < M; i++){
		sum += fn(x[i], y[i]);
	}
	return sum;
}

//shorthand sum('x * y') == sumxy(function(x,y){return x * y})
function sum(fnsrc){
	return sumxy(new Function('x,y', 'return '+fnsrc));
}

var w1 = (
		M * sum('x * y') - sum('x') * sum('y')
	)/(
		M * sum('x * x') - Math.pow(sum('x'), 2)
	);
var w0 = sum('y') / M - w1/M * sum('x');

"y = "+w1+"x + "+w0

//here's the implmentation without eval.

var w1 = (
		M * sumxy(function(x,y){return x * y}) - sumxy(function(x,y){return x})*sumxy(function(x,y){return y})
	)/(
		M * sumxy(function(x,y){return x*x}) - Math.pow(sumxy(function(x,y){return x}), 2)
	);
var w0 = sumxy(function(x,y){return y}) / M - w1/M * sumxy(function(x,y){return x});

"y = "+w1+"x + "+w0

seems simple.

w1 is... (4 * (2+6+12+20) - 10_14) / (4 * (1+4+9+16) - 10_10)) = 1.
w0 is... 14 / 4 - (1 / 4 * 10) = 1

Cool, it works! (even though I have no idea what it's doing) I'm going to look this over tomorrow because I need to stop procrastinating!!!!!!