support the specification of a combined EEG and MEG volume conduction model as a cell array

See also http://bugzilla.fieldtriptoolbox.org/show_bug.cgi?id=3089 and
http://bugzilla.fieldtriptoolbox.org/show_bug.cgi?id=2684

Author: robertoostenveld

fileio/private/ft_datatype_headmodel.m

@@ -96,6 +96,15 @@
   return;
 end
 
+if iscell(headmodel)
+  % this might represent combined EEG, ECoG and/or MEG
+  for i=1:numel(headmodel)
+    % call recursively
+    headmodel{i} = ft_datatype_headmodel(headmodel{i}, varargin{:});
+  end
+  return
+end
+
 switch version
 
   case '2015'

forward/ft_convert_units.m

@@ -19,9 +19,9 @@
 % are specified, this function will only determine the native geometrical
 % units of the object.
 %
-% See FT_ESTIMATE_UNITS, FT_READ_VOL, FT_READ_SENS
+% See also FT_ESTIMATE_UNITS, FT_READ_VOL, FT_READ_SENS
 
-% Copyright (C) 2005-2013, Robert Oostenveld
+% Copyright (C) 2005-2016, Robert Oostenveld
 %
 % This file is part of FieldTrip, see http://www.fieldtriptoolbox.org
 % for the documentation and details.
@@ -59,6 +59,13 @@
   end
   obj = tmp;
   return
+elseif iscell(obj) && numel(obj)>1
+  % deal with a cell array
+  % this might represent combined EEG, ECoG and/or MEG
+  for i=1:numel(obj)
+    obj{i} = ft_convert_units(obj{i}, target, varargin{:});
+  end
+  return
 end
 
 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

forward/ft_prepare_vol_sens.m

@@ -58,6 +58,14 @@
 %
 % $Id$
 
+if iscell(headmodel) && iscell(sens)
+  % this represents combined EEG, ECoG and/or MEG
+  for i=1:numel(headmodel)
+    [headmodel{i}, sens{i}] = ft_prepare_vol_sens(headmodel{i}, sens{i}, varargin{:});
+  end
+  return
+end
+
 % get the optional input arguments
 % fileformat = ft_getopt(varargin, 'fileformat');
 channel = ft_getopt(varargin, 'channel', sens.label);   % cell-array with channel labels, default is all
@@ -357,9 +365,9 @@
 
     case {'slab_monopole'}
       % electrodes' all-to-all distances
-      numel  = size(sens.elecpos,1);
-      ref_el = sens.elecpos(1,:);
-      md  = dist( (sens.elecpos-repmat(ref_el,[numel 1]))' );
+      numelc  = size(sens.elecpos,1);
+      ref_elc = sens.elecpos(1,:);
+      md  = dist( (sens.elecpos-repmat(ref_elc,[numelc 1]))' );
       % choose min distance between electrodes
       md  = min(md(1,2:end));
       pos = sens.elecpos;

forward/private/ft_datatype_headmodel.m

@@ -96,6 +96,15 @@
   return;
 end
 
+if iscell(headmodel)
+  % this might represent combined EEG, ECoG and/or MEG
+  for i=1:numel(headmodel)
+    % call recursively
+    headmodel{i} = ft_datatype_headmodel(headmodel{i}, varargin{:});
+  end
+  return
+end
+
 switch version
 
   case '2015'

private/ft_fetch_vol.m

@@ -10,7 +10,7 @@
 %
 % See also FT_READ_VOL, FT_FETCH_DATA
 
-% Copyright (C) 2011, Jörn M. Horschig
+% Copyright (C) 2011, J?rn M. Horschig
 %
 % This file is part of FieldTrip, see http://www.fieldtriptoolbox.org
 % for the documentation and details.
@@ -41,6 +41,9 @@
   headmodel = ft_read_vol(cfg.headmodel);
 elseif isfield(cfg, 'headmodel') && (isstruct(cfg.headmodel) || isa(cfg.headmodel, 'config'))
   headmodel = cfg.headmodel;
+elseif isfield(cfg, 'headmodel') && iscell(cfg.headmodel) 
+  % this might represent combined EEG, ECoG and/or MEG
+  headmodel = cfg.headmodel;
 else
   error('no headmodel specified');
 end

private/prepare_headmodel.m

@@ -87,11 +87,20 @@
 end
 
 % ensure that these are a struct, which may be required in case configuration tracking is used
-headmodel  = struct(headmodel);
-sens = struct(sens);
+% FIXME this fails for combined EEG+MEG
+% headmodel = struct(headmodel);
+% sens      = struct(sens);
 
 % the prepare_vol_sens function from the forwinv module does most of the actual work
 [headmodel, sens] = ft_prepare_vol_sens(headmodel, sens, 'channel', cfg.channel, 'order', cfg.order);
 
 % update the selected channels in the configuration
-cfg.channel = sens.label;
+if iscell(sens)
+  % this represents combined EEG, ECoG and/or MEG
+  cfg.channel = {};
+  for i=1:numel(sens)
+    cfg.channel = cat(1, cfg.channel, sens{i}.label(:));
+  end
+else
+  cfg.channel = sens.label;
+end