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

  FT_DATATYPE determines the type of data represented in a FieldTrip data
  structure and returns a string with raw, freq, timelock source, comp,
  spike, source, volume, dip, montage, event.
 
  Use as
    [type, dimord] = ft_datatype(data)
    [status]       = ft_datatype(data, desired)
 
  See also FT_DATATYPE_COMP, FT_DATATYPE_FREQ, FT_DATATYPE_MVAR,
  FT_DATATYPE_SEGMENTATION, FT_DATATYPE_PARCELLATION, FT_DATATYPE_SOURCE,
  FT_DATATYPE_TIMELOCK, FT_DATATYPE_DIP, FT_DATATYPE_HEADMODEL,
  FT_DATATYPE_RAW, FT_DATATYPE_SENS, FT_DATATYPE_SPIKE, FT_DATATYPE_VOLUME