.", 32, 612);
	}

	// draw interpolation
	if(canvas_name == "interpolation_canvas") {
		if(points.length > 0) {
			var polynomial = interpolation_of(points);

			context.beginPath();
			for(var j = 0; j < w; ++j){
				x = j;
				y = polynomial(x);
				if(j == 0)
					context.moveTo(x, y);
				else
					context.lineTo(x, y);
			}
			context.strokeStyle="#457fd6";
			context.stroke();
			context.closePath();
		}
		write_interpolation_formula();
	}

	// draw approximation + interpolation
	if(canvas_name == "bo