def get_xy(self, yidx, xidx=0):
        """
        Return stored data for the given indices for plot

        :param yidx: the indices of the y-axis variables(1-indexing)
        :param xidx: the index of the x-axis variables
        :return: None
        """
        assert isinstance(xidx, int)
        if isinstance(yidx, int):
            yidx = [yidx]

        t_vars = self.concat_t_vars()

        xdata = t_vars[:, xidx]
        ydata = t_vars[:, yidx]

        return xdata.tolist(), ydata.transpose().tolist()
Return stored data for the given indices for plot

        :param yidx: the indices of the y-axis variables(1-indexing)
        :param xidx: the index of the x-axis variables
        :return: None