def lapnumber_axis(ax, axis='xaxis'):
    """Set axis to integer ticks only."

    Args:
        ax: matplotlib axis
        axis (='xaxis', optional): can be 'xaxis' or 'yaxis'

    Returns:
        the modified axis instance

    """
    getattr(ax, axis).get_major_locator().set_params(integer=True, min_n_ticks=0)

    return ax