def set_y_axis_min(vsc):
    """
    Determine whether y_axis_min should be zero or a negative value

    Parameters
    ----------
    vsc: Pandas Series

    Returns
    -------
    zero or 1.1 * negative minimum of the series
    """
    if vsc.min() > 0:
        y_axis_min = 0
    else:
        y_axis_min = 1.1 * vsc.min()

    return y_axis_min