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

```  FT_DATATYPE_PARCELLATION describes the FieldTrip MATLAB structure for parcellated
cortex-based data and atlases. A parcellation can either be indexed or probabilistic
(see below).

A parcellation describes the tissue types for each of the surface elements.
Parcellations are often, but not always labeled. A parcellatoin can be used to
estimate the activity from MEG data in a known region of interest. A surface-based
atlas is basically a very detailled parcellation with an anatomical label for each
vertex.

An example of a surface based Brodmann parcellation looks like this

pos: [8192x3]         positions of the vertices forming the cortical sheet
tri: [16382x3]        triangles of the cortical sheet
coordsys: 'ctf'            the (head) coordinate system in which the vertex positions are expressed
unit: 'mm'             the units in which the coordinate system is expressed
brodmann: [8192x1 uint8]   values from 1 to N, the value 0 means unknown
brodmannlabel: {Nx1 cell}

An alternative representation of this parcellation is

pos: [8192x3]           positions of the vertices forming the cortical sheet
tri: [16382x3]          triangles of the cortical sheet
coordsys: 'ctf'              the (head) coordinate system in which the vertex positions are expressed
unit: 'mm'               the units in which the coordinate system is expressed
Brodmann_Area_1: [8192x1 logical]   binary map representing the voxels belonging to the specific area
Brodmann_Area_2: [8192x1 logical]   binary map representing the voxels belonging to the specific area
Brodmann_Area_3: [8192x1 logical]   binary map representing the voxels belonging to the specific area
...

The examples above demonstrate that a parcellation can be indexed, i.e. consisting of
subsequent integer numbers (1, 2, ...) or probabilistic, consisting of real numbers
ranging from 0 to 1 that represent probabilities between 0% and 100%. An extreme case
is one where the probability is either 0 or 1, in which case the probability can be
represented as a binary or logical array.

The only difference to the source data structure is that the parcellation structure
contains the additional fields xxx and xxxlabel. See FT_DATATYPE_SOURCE for further
details.

- pos

Optional fields:
- tri, coordsys, unit

Deprecated fields:
- none

Obsoleted fields:
- none

Revision history:
(2012/latest) The initial version was defined in accordance with the representation of
a voxel-based segmentation.