def sline_(self, window_size=5,
			   y_label="Moving average", chart_label=None):
		"""
		Get a moving average curve chart to smooth between points
		"""
		options = dict(window_size=window_size, y_label=y_label)
		try:
			return self._get_chart("sline", style=self.chart_style,
								   opts=self.chart_opts, label=chart_label,
								   options=options)
		except Exception as e:
			self.err(e, self.sline_, "Can not draw smooth curve chart")
Get a moving average curve chart to smooth between points