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

  FT_FREQGRANDAVERAGE computes the average powerspectrum or time-frequency spectrum
  over multiple subjects
  Use as
    [grandavg] = ft_freqgrandaverage(cfg, freq1, freq2, freq3...)
  The input data freq1..N are obtained from either FT_FREQANALYSIS with
  keeptrials=no or from FT_FREQDESCRIPTIVES. The configuration structure
  can contain
    cfg.keepindividual = 'yes' or 'no' (default = 'no')
    cfg.foilim         = [fmin fmax] or 'all', to specify a subset of frequencies (default = 'all')
    cfg.toilim         = [tmin tmax] or 'all', to specify a subset of latencies (default = 'all')        = Nx1 cell-array with selection of channels (default = 'all'),
                         see FT_CHANNELSELECTION for details
    cfg.parameter      = string or cell-array of strings indicating which
                         parameter(s) to average. default is set to
                         'powspctrm', if it is present in the data.
  To facilitate data-handling and distributed computing you can use
    cfg.inputfile   =  ...
    cfg.outputfile  =  ...
  If you specify one of these (or both) the input data will be read from a *.mat
  file on disk and/or the output data will be written to a *.mat file. These mat
  files should contain only a single variable, corresponding with the
  input/output structure. For this particular function, the input should be
  specified as a cell array.