def resample_signal(self, data_frame):
        """
            Convenience method for frequency conversion and resampling of data frame. 
            Object must have a DatetimeIndex. After re-sampling, this methods interpolate the time magnitude sum 
            acceleration values and the x,y,z values of the data frame acceleration

            :param data_frame: the data frame to resample
            :type data_frame: pandas.DataFrame
            :return: the resampled data frame
            :rtype: pandas.DataFrame

        """
        df_resampled = data_frame.resample(str(1 / self.sampling_frequency) + 'S').mean()

        f = interpolate.interp1d(data_frame.td, data_frame.mag_sum_acc)
        new_timestamp = np.arange(data_frame.td[0], data_frame.td[-1], 1.0 / self.sampling_frequency)
        df_resampled.mag_sum_acc = f(new_timestamp)

        logging.debug("resample signal")
        return df_resampled.interpolate(method='linear')