def median_scaler(s):
    """
    Remove median, divide by IQR.
    """
    if sum(~np.isnan(s)) > 2:
        ss = s[~np.isnan(s)]
        median = np.median(ss)
        IQR = np.diff(np.percentile(ss, [25, 75]))
        return (s - median) / IQR
    else:
        return np.full(s.shape, np.nan)