 N = 500, if PAD = -1, we do not pad; if PAD = 0, we pad the FFT
                       to 512 points, if pad=1, we pad to 1024 points etc.
                       Defaults to 0.
        p            (P-value to calculate error bars for) - optional. 
                           Defaults to 0.05/N where N is data length.
       plt         (y/n for plot and no plot respectively) - plots the
       Fratio at all frequencies if y
       f0          frequencies at which you want to remove the
            