def calcperc_sym(b, perc=(0.1,99.9)):
    """
    Get symmetrical percentile values
    Useful for determining clim centered on 0 for difference maps
    """
    clim = np.max(np.abs(calcperc(b, perc)))
    #clim = (-clim, clim)
    return -clim, clim
Get symmetrical percentile values
    Useful for determining clim centered on 0 for difference maps