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

  FT_READ_DATA reads electrophysiological data from a variety of EEG, MEG and LFP
  files and represents it in a common data-independent format. The supported formats
  are listed in the accompanying FT_READ_HEADER function.
  Use as
    dat = ft_read_data(filename, ...)
  Additional options should be specified in key-value pairs and can be
    'header'         header structure, see FT_READ_HEADER
    'begsample'      first sample to read
    'endsample'      last sample to read
    'begtrial'       first trial to read, mutually exclusive with begsample+endsample
    'endtrial'       last trial to read, mutually exclusive with begsample+endsample
    'chanindx'       list with channel indices to read
    'chanunit'       cell-array with strings, the desired unit of each channel
    'checkboundary'  boolean, whether to check for reading segments over a trial boundary
    'checkmaxfilter' boolean, whether to check that maxfilter has been correctly applied (default = true)
    'cache'          boolean, whether to use caching for multiple reads
    'dataformat'     string
    'headerformat'   string
    'fallback'       can be empty or 'biosig' (default = [])
    'blocking'       wait for the selected number of events (default = 'no')
    'timeout'        amount of time in seconds to wait when blocking (default = 5)
  This function returns a 2-D matrix of size Nchans*Nsamples for continuous
  data when begevent and endevent are specified, or a 3-D matrix of size
  Nchans*Nsamples*Ntrials for epoched or trial-based data when begtrial
  and endtrial are specified.
  The list of supported file formats can be found in FT_READ_HEADER.
  To use an external reading function, you can specify the function name as argument
  to 'dataformat'. The function needs to be on the path, and should take as input:
  filename, hdr, begsample, endsample, chanindx.