EEG positions are mapped to outermost head surface
[Xout, IX, DD] = vb_map_eeg_to_head(X,Vs,BEM,dx,Np)
X : sensor coordinate (センサー座標) [Neeg x 3]
Vs : vertex coordinate on the boudary surface (境界面座標) [Nv x 3]
BEM.Nvertex = start & end vertex index for n-th closed surface
= [ start_id(1) end_id(1) ;
... ;
start_id(Nsurf) end_id(Nsurf) ]
innermost to outermost
= 各境界面の頂点インデックス
= [開始インデックス, 終了インデックス]
dx : neighbor points are searched within dx (m) from nearest point
Np : Np points are searched for each sensor position
IX : Vertex index nearest to EEG sensor [Neeg x Np]
DD : Distance from EEG sensor to head vertex [Neeg x Np]
Xout : Nearest head vertex point to EEG sensor;
2007-12-25 M. Sato
Copyright (C) 2011, ATR All Rights Reserved.
License : New BSD License(see VBMEG_LICENSE.txt)0001 function [Xout, IX, DD] = vb_map_eeg_to_head(X,Vs,BEM,dx,Np) 0002 % EEG positions are mapped to outermost head surface 0003 % [Xout, IX, DD] = vb_map_eeg_to_head(X,Vs,BEM,dx,Np) 0004 % X : sensor coordinate (センサー座標) [Neeg x 3] 0005 % Vs : vertex coordinate on the boudary surface (境界面座標) [Nv x 3] 0006 % BEM.Nvertex = start & end vertex index for n-th closed surface 0007 % = [ start_id(1) end_id(1) ; 0008 % ... ; 0009 % start_id(Nsurf) end_id(Nsurf) ] 0010 % innermost to outermost 0011 % = 各境界面の頂点インデックス 0012 % = [開始インデックス, 終了インデックス] 0013 % dx : neighbor points are searched within dx (m) from nearest point 0014 % Np : Np points are searched for each sensor position 0015 % 0016 % IX : Vertex index nearest to EEG sensor [Neeg x Np] 0017 % DD : Distance from EEG sensor to head vertex [Neeg x Np] 0018 % Xout : Nearest head vertex point to EEG sensor; 0019 % 2007-12-25 M. Sato 0020 % 0021 % Copyright (C) 2011, ATR All Rights Reserved. 0022 % License : New BSD License(see VBMEG_LICENSE.txt) 0023 0024 DEBUG = 0; 0025 Rmax = 1000; 0026 0027 if ~exist('dx','var'), dx = 0.02; end; % 20 mm 0028 if ~exist('Np','var'), Np = 3; end; 0029 0030 % 変数の次元 0031 Neeg = size(X,1); % # of EEG sensor 0032 IX = zeros(Neeg,Np); 0033 DD = repmat(Rmax,[Neeg,Np]); 0034 0035 % Find outermost head vertex near EEG position 0036 0037 % Vertex index for outermost surface 0038 Nsurf = size(BEM.Nvertex,1); % 境界面の数 0039 ix_head = BEM.Nvertex(Nsurf,1):BEM.Nvertex(Nsurf,2); 0040 0041 % Vertex for outermost surface 0042 V = Vs(ix_head,:); 0043 0044 if DEBUG==1, V = Vs; end; 0045 0046 for n=1:Neeg 0047 % センサに最も近い境界面頂点探索 0048 dd = sqrt((V(:,1)-X(n,1)).^2 + (V(:,2)-X(n,2)).^2 + (V(:,3)-X(n,3)).^2); 0049 dmin = min(dd); 0050 0051 ix = find( dd <= (dmin + dx)); 0052 Nx = length(ix); 0053 [d, jx] = sort(dd(ix)); 0054 0055 if Nx > Np, 0056 jx = jx(1:Np); 0057 IX(n,:) = ix_head(ix(jx)); 0058 DD(n,:) = d(1:Np)'; 0059 else 0060 IX(n,1:Nx) = ix_head(ix(jx)); 0061 DD(n,1:Nx) = d'; 0062 end; 0063 0064 end 0065 0066 Xout = Vs(IX(:,1),:);