FieldTrip

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

  FT_FREQANALYSIS_MTMWELCH performs frequency analysis on any time series
  trial data using the 'multitaper method' (MTM) based on discrete
  prolate spheroidal sequences (Slepian sequences) as tapers. Alternatively,
  you can use conventional tapers (e.g. Hanning).
  
  Besides multitapering, this function uses Welch's averaged, modified
  periodogram method. The data is divided into a number of sections with
  overlap, each section is windowed with the specified taper(s) and the
  powerspectra are computed and averaged over the sections in each trial.
 
  Use as
    [freq] = ft_freqanalysis(cfg, data)
 
  The data should be organised in a structure as obtained from
  the FT_PREPROCESSING function. The configuration should be according to
    cfg.method     = method used for frequency or time-frequency decomposition
                     see FT_FREQANALYSIS for details
    cfg.output     = 'pow'       return the power-spectra
                     'powandcsd' return the power and the cross-spectra
    cfg.taper      = 'dpss', 'hanning' or many others, see WINDOW (default = 'dpss')
 
  For cfg.output='powandcsd', you should specify the channel combinations
  between which to compute the cross-spectra as cfg.channelcmb. Otherwise
  you should specify only the channels in cfg.channel.
  
    cfg.channel    = Nx1 cell-array with selection of channels (default = 'all'),
                     see FT_CHANNELSELECTION for details
    cfg.channelcmb = Mx2 cell-array with selection of channel pairs (default = {'all' 'all'}),
                     see FT_CHANNELCOMBINATION for details
 
  This function uses FT_FREQANALYSIS_MTMCONVOL for the low-level
  computations, and you can use the options of that function to specify
  the length of the time windows, the amount of overlap, and the amount
  of spectral smoothing (in case of dpss tapers) per window.
 
    cfg.foi        = vector 1 x numfoi, frequencies of interest
    cfg.t_ftimwin  = vector 1 x numfoi, length of time window (in seconds)
    cfg.tapsmofrq  = vector 1 x numfoi, the amount of spectral smoothing through
                     multi-tapering. Note that 4 Hz smoothing means
                     plus-minus 4 Hz, i.e. a 8 Hz smoothing box.
    cfg.toi        = vector 1 x numtoi, the times on which the analysis windows 
                     should be centered (in seconds)
    cfg.trials     = 'all' or a selection given as a 1xN vector (default = 'all')
    cfg.keeptrials = 'yes' or 'no', return individual trials or average (default = 'no')
    cfg.keeptapers = 'yes' or 'no', return individual tapers or average (default = 'no')
    cfg.pad        = number or 'maxperlen', length in seconds to which the data can be padded out (default = 'maxperlen')
 
  See also FT_FREQANALYSIS_MTMCONVOL, FT_FREQANALYSIS