function xRange(mouseX) {
	var vm = this._view;
	return vm ? (Math.abs(mouseX - vm.x) < vm.radius + vm.hitRadius) : false;
}
Gets the tooltip position nearest of the item nearest to the event position
@function Chart.Tooltip.positioners.nearest
@param elements {Chart.Element[]} the tooltip elements
@param eventPosition {Point} the position of the event in canvas coordinates
@returns {Point} the tooltip position