def get_xname(self, var, coords=None):
        """Get the name of the x-dimension

        This method gives the name of the x-dimension (which is not necessarily
        the name of the coordinate if the variable has a coordinate attribute)

        Parameters
        ----------
        var: xarray.Variables
            The variable to get the dimension for
        coords: dict
            The coordinates to use for checking the axis attribute. If None,
            they are not used

        Returns
        -------
        str
            The coordinate name

        See Also
        --------
        get_x"""
        if coords is not None:
            coord = self.get_variable_by_axis(var, 'x', coords)
            if coord is not None and coord.name in var.dims:
                return coord.name
        dimlist = list(self.x.intersection(var.dims))
        if dimlist:
            if len(dimlist) > 1:
                warn("Found multiple matches for x coordinate in the variable:"
                     "%s. I use %s" % (', '.join(dimlist), dimlist[0]),
                     PsyPlotRuntimeWarning)
            return dimlist[0]
        # otherwise we return the coordinate in the last position
        return var.dims[-1]