def icrosscorr(lag,ts0, ts1):
    """ Lag-N cross correlation. 
    Shifted data filled with NaNs 
    
    Parameters
    ----------
    lag : int, default 0
    ts0, ts1 : pandas.Series objects of equal length
    Returns
    ----------
    crosscorr : float
    """
    return ts0.corr(ts1.shift(int(lag)))