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

  FT_DATATYPE_FREQ describes the FieldTrip MATLAB structure for freq data
 
  The freq data structure represents frequency or time-frequency decomposed
  channel-level data. This data structure is usually generated with the
  FT_FREQANALYSIS function.
 
  An example of a freq data structure containing the powerspectrum for 306 channels
  and 120 frequencies is
 
        dimord: 'chan_freq'          defines how the numeric data should be interpreted
     powspctrm: [306x120 double]     the power spectum
         label: {306x1 cell}         the channel labels
          freq: [1x120 double]       the frequencies expressed in Hz
           cfg: [1x1 struct]         the configuration used by the function that generated this data structure
 
  An example of a freq data structure containing the time-frequency resolved
  spectral estimates of power (i.e. TFR) for 306 channels, 120 frequencies
  and 60 timepoints is
 
        dimord: 'chan_freq_time'     defines how the numeric data should be interpreted
     powspctrm: [306x120x60 double]  the power spectum
         label: {306x1 cell}         the channel labels
          freq: [1x120 double]       the frequencies, expressed in Hz
          time: [1x60 double]        the time, expressed in seconds
           cfg: [1x1 struct]         the configuration used by the function that generated this data structure
 
  Required fields:
    - label, dimord, freq
 
  Optional fields:
    - powspctrm, fouriesspctrm, csdspctrm, cohspctrm, time, labelcmb, grad, elec, cumsumcnt, cumtapcnt, trialinfo
 
  Deprecated fields:
    - <none>
 
  Obsoleted fields:
    - <none>
 
  Revision history:
 
  (2011/latest) The description of the sensors has changed, see FT_DATATYPE_SENS
  for further information.
 
  (2008) The presence of labelcmb in case of crsspctrm became optional,
  from now on the crsspctrm can also be represented as Nchan * Nchan.
 
  (2006) The fourierspctrm field was added as alternative to powspctrm and
  crsspctrm. The fields foi and toi were renamed to freq and time.
 
  (2003v2) The fields sgn and sgncmb were renamed into label and labelcmb.
 
  (2003v1) The initial version was defined.
 
  See also FT_DATATYPE, FT_DATATYPE_COMP, FT_DATATYPE_DIP, FT_DATATYPE_FREQ,
  FT_DATATYPE_MVAR, FT_DATATYPE_RAW, FT_DATATYPE_SOURCE, FT_DATATYPE_SPIKE,
  FT_DATATYPE_TIMELOCK, FT_DATATYPE_VOLUME