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

  FT_SOURCEWRITE exports source-reconstructed results to gifti or nifti format file.
  The appropriate output file depends on whether the source locations are described by
  on a cortically constrained sheet (gifti) or by a regular 3D lattice (nifti).
  Use as
   ft_sourcewrite(cfg, source)
  where source is a source structure obtained from FT_SOURCEANALYSIS and
  cfg is a structure that should contain
   cfg.filename  = string, filename without the extension
   cfg.filetype  = string, can be 'nifti', 'gifti' or 'cifti' (default is automatic)
   cfg.parameter = string, functional parameter to be written to file
   cfg.precision = string, can be 'single', 'double', etc.
  To facilitate data-handling and distributed computing you can use
    cfg.inputfile   =  ...
  If you specify this the input data will be read from a *.mat
  file on disk. This mat file should contain only a single variable,
  corresponding with the input data structure.