Note that this reference documentation is identical to the help that is displayed in MATLAB when you type “help ft_preproc_derivative”.

  FT_PREPROC_DERIVATIVE computes the temporal Nth order derivative of the
  data
 
  Use as
    [dat] = ft_preproc_derivative(dat, order)
  where
    dat        data matrix (Nchans X Ntime)
    order      number representing the Nth derivative (default = 1)
 
  See also PREPROC