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

  FT_WRITE_DATA exports electrophysiological data such as EEG to a file. 
 
  Use as
    ft_write_data(filename, dat, ...)
 
  The specified filename can contain the filename extension. If it has no filename
  extension not, it will be added automatically.
 
  Additional options should be specified in key-value pairs and can be
    'header'         header structure that describes the data, see FT_READ_HEADER
    'dataformat'     string, see below
    'append'         boolean, not supported for all formats
    'chanindx'       1xN array
 
  The supported dataformats are
    edf
    gdf
    brainvision_eeg
    neuralynx_ncs
    neuralynx_sdma
    plexon_nex
    riff_wave
    fcdc_matbin
    fcdc_mysql
    fcdc_buffer
    matlab
 
  For EEG data formats, the input data is assumed to be scaled in microvolt.
 
  See also FT_READ_HEADER, FT_READ_DATA, FT_READ_EVENT, FT_WRITE_EVENT