def _points(self, x_pos):
        """
        Convert given data values into drawable points (x, y)
        and interpolated points if interpolate option is specified
        """
        for serie in self.all_series:
            serie.points = [(x_pos[i], v) for i, v in enumerate(serie.values)]
            if serie.points and self.interpolate:
                serie.interpolated = self._interpolate(x_pos, serie.values)
            else:
                serie.interpolated = []
Convert given data values into drawable points (x, y)
        and interpolated points if interpolate option is specified