def load_transform_parameters(self):
		"Cache the parameters necessary to transform x & y coordinates"
		x_min, x_max, x_div = self.x_range()
		y_min, y_max, y_div = self.y_range()
		x_step = (float(self.graph_width) - self.font_size * 2) / \
			(x_max - x_min)
		y_step = (float(self.graph_height) - self.font_size * 2) / \
			(y_max - y_min)
		self.__transform_parameters = dict(locals())
		del self.__transform_parameters['self']
Cache the parameters necessary to transform x & y coordinates