LinReg.as

package {
	public class LinReg {
		private var Sx:Number=0;
		private var Sy:Number=0;
		private var Sxy:Number=0;
		private var Sxx:Number=0;
		private var n:uint=0;

		public function add(x:Number,y:Number):void {
			n++;
			Sx+=x;
			Sy+=y;
			Sxy+=x*y;
			Sxx+=x*x;
		}

		private var _n:uint=0;
		private var _a:Number=0;
		private var _b:Number=0;

		public function get(x:Number):Number {
			if(_n!=n) {
				if(n==1)
					_b=0;
				else
					_b=(n*Sxy-Sx*Sy)/(n*Sxx-Sx*Sx);
				_a=Sy/n-_b*Sx/n;
				_n=n;
			}
			return _a+_b*x;
		}
	}
}