FT_WRITE_CIFTI writes functional data or functional connectivity to a cifti-2
 file. The geometrical description of the brainordinates can consist of
 triangulated surfaces or voxels in a regular 3-D volumetric grid. The functional
 data can consist of a dense or a parcellated representation. Furthermore, it
 writes the geometrical description of the surfaces to one or multiple gifti
 files.

 Use as
   ft_write_cifti(filename, data, ...)
 where the filename is a string and the data according to the description below.

 If the input data describes a dense representation of functional data, the data
 structure should conform to the FT_DATATYPE_SOURCE or FT_DATATYPE_VOLUME
 definition.

 If the input data describes a parcellated representation of functional data, the
 data structure should conform to the FT_DATATYPE_TIMELOCK or FT_DATATYPE_FREQ
 definition. In addition, the description of the geometry should be specified in
 the data.brainordinate field, which should conform to the FT_DATATYPE_SOURCE or
 FT_DATATYPE_VOLUME definition.

 Any optional input arguments should come in key-value pairs and may include
   'parameter'        = string, fieldname that contains the functional data
   'brainstructure'   = string, fieldname that describes the brain structures (default = 'brainstructure')
   'parcellation'     = string, fieldname that describes the parcellation (default = 'parcellation')
   'precision'        = string, can be 'single', 'double', 'int32', etc. (default ='single')
   'writesurface'     = boolean, can be false or true (default = true)
   'debug'            = boolean, write a debug.xml file (default = false)

 The brainstructure refers to the global anatomical structure, such as CortexLeft, Thalamus, etc.
 The parcellation refers to the the detailled parcellation, such as BA1, BA2, BA3, etc.

 See also FT_READ_CIFTI, FT_READ_MRI, FT_WRITE_MRI