def differentiate_timeseries(timeseries, diff_lag=1):
    """
    Differentiate a time-series signal.
    -------------------------------------------------------
    Args:
        timeseries : pd.DataFrame or pd.Series
            Pandas Series with time series to be differentiated
        diff_lag: int
            Time difference to use
    -------------------------------------------------------
    return:
        predictions_mean : pd.Series
            Differentiated time series

    """
    diff = timeseries.diff(diff_lag)
    return diff.fillna(0)