get_center_neuromag

 get neuromag sensor center position in head coordinate
  [pick,Qpick,Weight] = get_center_neuromag(ch_info)

    ch_info     @ channel information is including transform matrix
             .Nch      [double]
                 : The number of channels.
             .channel_ix   [Nch x 1 double]
                 : MEG channel name list.
             .sensort_type [Nch x 1 double]
                 : sensor type list
             .coil_type    {Nch x 1 cell}
                 : coil type string list
                   ex. coil_type{1} = 'VV_PLANAR_T1'
             .trans_coil2head   : {Nch x 1}
                 : transformation matrix (COIL  ==> HEAD)
                   trans_coil2head{n} = [4x4 double]
             .trans_coil2device : {Nch x 1}
                 : transformation matrix list (COIL  ==> DEVICE)
                   trans_coil2device{n} = [4x4 double]
             .trans_device2head : [4 x 4 double]
                 : transformation matrix (DEVICE  ==> HEAD)

  [rHead 1] = [rCoil 1] * ch_info.trans_coil2head{n}'

 Masa-aki Sato 2009-4-13

 Copyright (C) 2011, ATR All Rights Reserved.
 License : New BSD License(see VBMEG_LICENSE.txt)

0001 function    [pick,Qpick] = get_center_neuromag(ch_info)
0002 % get neuromag sensor center position in head coordinate
0003 %  [pick,Qpick,Weight] = get_center_neuromag(ch_info)
0004 %
0005 %    ch_info     @ channel information is including transform matrix
0006 %             .Nch      [double]
0007 %                 : The number of channels.
0008 %             .channel_ix   [Nch x 1 double]
0009 %                 : MEG channel name list.
0010 %             .sensort_type [Nch x 1 double]
0011 %                 : sensor type list
0012 %             .coil_type    {Nch x 1 cell}
0013 %                 : coil type string list
0014 %                   ex. coil_type{1} = 'VV_PLANAR_T1'
0015 %             .trans_coil2head   : {Nch x 1}
0016 %                 : transformation matrix (COIL  ==> HEAD)
0017 %                   trans_coil2head{n} = [4x4 double]
0018 %             .trans_coil2device : {Nch x 1}
0019 %                 : transformation matrix list (COIL  ==> DEVICE)
0020 %                   trans_coil2device{n} = [4x4 double]
0021 %             .trans_device2head : [4 x 4 double]
0022 %                 : transformation matrix (DEVICE  ==> HEAD)
0023 %
0024 %  [rHead 1] = [rCoil 1] * ch_info.trans_coil2head{n}'
0025 %
0026 % Masa-aki Sato 2009-4-13
0027 %
0028 % Copyright (C) 2011, ATR All Rights Reserved.
0029 % License : New BSD License(see VBMEG_LICENSE.txt)
0030 
0031 Nch = ch_info.Nch;
0032 
0033 % Coil position & direction
0034 pick  = zeros(Nch,3);
0035 Qpick = zeros(Nch,3);
0036 
0037 Ncoil = 0;
0038 Nchan = 0;
0039 
0040 % Head coordinate
0041 for n=1:Nch
0042     % Transformation matrix from coil -> head
0043     U = ch_info.trans_coil2head{n}';
0044     
0045     % Get coil position & direction
0046     % fixed coil position is defined for coil_type in Coil coordinate
0047     [pick1, Qpick1] = sensor_center_neuromag(ch_info.coil_type{n}, U);
0048     
0049     Npick  = size(pick1,1);
0050     
0051     if Npick > 0,
0052         
0053         % Coil position & direction
0054         ix = (1:Npick) + Ncoil;
0055         pick(ix ,:)    = pick1;
0056         Qpick(ix ,:) = Qpick1;
0057         
0058         % Coil -> Channel matrix index
0059         % Channel index
0060         Nchan = Nchan + 1;
0061         Ncoil = Ncoil + Npick;
0062     end
0063 end
0064 
0065 pick  = pick(1:Ncoil,:) ;
0066 Qpick = Qpick(1:Ncoil,:);