text.closePath();
	}

	// the axes
	function sharp(x) {return floor(x) + 0.5;}
	context.font = "14px Arial";
	context.fillStyle = "#444444";
	context.textAlign = "center";
	context.textBaseline = "middle";
	context.strokeStyle = "#000000";
	context.lineWidth = 1;
	context.beginPath();
	if(document.getElementById("scale_1").checked) {
		draw_arrow(context, 0, sharp(y2s(0)), w, sharp(y2s(0)), "#000000");
		draw_arrow(context, sharp(x2s(0)), h, sharp(x2s(0)), 0, "#000000");
		// horizontal
		for(var j = steppe