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+=====  FT_PREPARE_HEADMODEL =====
+Note that this reference documentation is identical to the help that is displayed in MATLAB when you type "help ft_prepare_headmodel".
+<html><pre>
+  <a href=/reference/ft_prepare_headmodel><font color=green>FT_PREPARE_HEADMODEL</font></a> constructs a volume conduction model from the geometry
+  of the head. The volume conduction model specifies how currents that are
+  generated by sources in the brain, e.g. dipoles, are propagated through the
+  tissue and how these result in externally measureable EEG potentials or MEG
+  fields.
+  FieldTrip implements a variety of forward solutions, partially with internal
+  code and some of them using external toolboxes or executables. Each of the
+  forward solutions requires a set of configuration options which are listed
+  below. This function takes care of all the preparatory steps in the
+  construction of the volume conduction model and sets it up so that
+  subsequent computations are efficient and fast.
+  Use as
+    headmodel = ft_prepare_headmodel(cfg)       or
+    headmodel = ft_prepare_headmodel(cfg, mesh) with the output of <a href=/reference/ft_prepare_mesh><font color=green>FT_PREPARE_MESH</font></a> or <a href=/reference/ft_read_headshape><font color=green>FT_READ_HEADSHAPE</font></a>
+    headmodel = ft_prepare_headmodel(cfg, seg)  with the output of <a href=/reference/ft_volumesegment><font color=green>FT_VOLUMESEGMENT</font></a>
+    headmodel = ft_prepare_headmodel(cfg, elec) with the output of <a href=/reference/ft_read_sens><font color=green>FT_READ_SENS</font></a>
+    headmodel = ft_prepare_headmodel(cfg, grid) with the output of <a href=/reference/ft_prepare_leadfield><font color=green>FT_PREPARE_LEADFIELD</font></a>
+  In general the input to this function is a geometrical description of the
+  shape of the head and a description of the electrical conductivity. The
+  geometrical description can be a set of surface points obtained from
+  fT_READ_HEADSHAPE, a surface mesh that was obtained from <a href=/reference/ft_prepare_mesh><font color=green>FT_PREPARE_MESH</font></a> or
+  a segmented anatomical MRI that was obtained from <a href=/reference/ft_volumesegment><font color=green>FT_VOLUMESEGMENT</font></a>.
+  The cfg argument is a structure that can contain:
+    cfg.method         string that specifies the forward solution, see below
+    cfg.conductivity   a number or a vector containing the conductivities of the compartments
+    cfg.tissue         a string or integer, to be used in combination with a 'seg' for the
+                       second intput. If 'brain', 'skull', and 'scalp' are fields
+                       present in 'seg', then cfg.tissue need not be specified, as
+                       these are defaults, depending on cfg.method. Otherwise,
+                       cfg.tissue should refer to which field(s) of seg should be used.
+  For EEG the following methods are available:
+    singlesphere       analytical single sphere model
+    concentricspheres  analytical concentric sphere model with up to 4 spheres
+    openmeeg           boundary element method, based on the OpenMEEG software
+    bemcp              boundary element method, based on the implementation from Christophe Phillips
+    dipoli             boundary element method, based on the implementation from Thom Oostendorp
+    asa                boundary element method, based on the (commercial) ASA software
+    simbio             finite element method, based on the SimBio software
+    fns                finite difference method, based on the FNS software
+    infinite           electric dipole in an infinite homogenous medium
+    halfspace          infinite homogenous medium on one side, vacuum on the other
+    besa               finite element leadfield matrix from BESA
+    interpolate        interpolate the precomputed leadfield
+  For MEG the following methods are available:
+    openmeeg           boundary element method, based on the OpenMEEG software
+    singlesphere       analytical single sphere model
+    localspheres       local spheres model for MEG, one sphere per channel
+    singleshell        realisically shaped single shell approximation, based on the implementation from Guido Nolte
+    infinite           magnetic dipole in an infinite vacuum
+  Each specific method has its own specific configuration options which are listed below.
+  BEMCP, DIPOLI, OPENMEEG
+    cfg.tissue            see above; in combination with 'seg' input
+    cfg.isolatedsource    (optional)
+  CONCENTRICSPHERES
+    cfg.tissue            see above; in combination with 'seg' input
+    cfg.fitind            (optional)
+  LOCALSPHERES
+    cfg.grad
+    cfg.tissue            see above; in combination with 'seg' input; default options are 'brain' or 'scalp'
+    cfg.feedback          (optional)
+    cfg.radius            (optional)
+    cfg.maxradius         (optional)
+    cfg.baseline          (optional)
+  SIMBIO
+    cfg.conductivity
+  SINGLESHELL
+    cfg.tissue            see above; in combination with 'seg' input; default options are 'brain' or 'scalp'
+  SINGLESPHERE
+    cfg.tissue            see above; in combination with 'seg' input; default options are 'brain' or 'scalp'; must be only 1 value
+  INTERPOLATE
+     cfg.outputfile       (required) string, filename prefix for the output files
+  BESA
+    cfg.headmodel         (required) string, filename of precomputed FEM leadfield
+    cfg.elecfile          (required) string, filename of electrode configuration for the FEM leadfield
+    cfg.outputfile        (required) string, filename prefix for the output files
+  FNS
+    cfg.tissue
+    cfg.tissueval
+    cfg.conductivity
+    cfg.elec
+    cfg.grad
+    cfg.transform
+    cfg.unit
+  HALFSPACE
+    cfg.point
+    cfg.submethod         (optional)
+  More details for each of the specific methods can be found in the corresponding
+  low-level function which is called FT_HEADMODEL_XXX where XXX is the method
+  of choise.
+  See also <a href=/reference/ft_prepare_sourcemodel><font color=green>FT_PREPARE_SOURCEMODEL</font></a>, <a href=/reference/ft_prepare_leadfield><font color=green>FT_PREPARE_LEADFIELD</font></a>, <a href=/reference/ft_prepare_mesh><font color=green>FT_PREPARE_MESH</font></a>,
+  <a href=/reference/ft_headmodel_bemcp><font color=green>FT_HEADMODEL_BEMCP</font></a>, <a href=/reference/ft_headmodel_asa><font color=green>FT_HEADMODEL_ASA</font></a>, <a href=/reference/ft_headmodel_dipoli><font color=green>FT_HEADMODEL_DIPOLI</font></a>,
+  <a href=/reference/ft_headmodel_simbio><font color=green>FT_HEADMODEL_SIMBIO</font></a>, <a href=/reference/ft_headmodel_fns><font color=green>FT_HEADMODEL_FNS</font></a>, <a href=/reference/ft_headmodel_halfspace><font color=green>FT_HEADMODEL_HALFSPACE</font></a>,
+  <a href=/reference/ft_headmodel_infinite><font color=green>FT_HEADMODEL_INFINITE</font></a>, <a href=/reference/ft_headmodel_openmeeg><font color=green>FT_HEADMODEL_OPENMEEG</font></a>, <a href=/reference/ft_headmodel_singlesphere><font color=green>FT_HEADMODEL_SINGLESPHERE</font></a>,
+  <a href=/reference/ft_headmodel_concentricspheres><font color=green>FT_HEADMODEL_CONCENTRICSPHERES</font></a>, <a href=/reference/ft_headmodel_localspheres><font color=green>FT_HEADMODEL_LOCALSPHERES</font></a>,
+  <a href=/reference/ft_headmodel_singleshell><font color=green>FT_HEADMODEL_SINGLESHELL</font></a>, <a href=/reference/ft_headmodel_interpolate><font color=green>FT_HEADMODEL_INTERPOLATE</font></a>
+</pre></html>