eeg_lap_hjorth.m

Matlab下的EEG处理程序库

function [Hjorth] = eeg_lap_hjorth(voltage,X,Y)
% EEG_LAP_HJORTH - 2D Laplacian of Potential at XY
%
% Useage:   [Hjorth] = eeg_lap_hjorth(voltage [,X,Y])
%
% Notes:    The Hjorth nearest neighbour, finite difference Laplacian.
%           For a continuous approximation of the Laplacian, use the
%           'eeg_lap' function.
%
%           This routine employs the del2 matlab command, which requires
%           'voltage' to be a rectangular matrix.  See 'help del2'.
%
% refs:     Hjorth B (1975).  An on-line transformation of EEG scalp
%             potentials into orthogonal source derivations. 
%             Electroencephalography & Clinical Neurophysiology, 39: 526-530.
%

% $Revision: 1.2 $ $Date: 2003/03/02 03:20:43 $

% Licence:  GNU GPL, no implied or express warranties
% History:  06/01, [e-mail]
%
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

    if ~exist('X','var') X = 1; end
    if ~exist('X','var') Y = 1; end

    Hjorth = 4*del2(voltage,X,Y);
    
    return
    
%[x,y] = meshgrid(-1:.25:1)
%z = (x.^2).*(y.^2)
%surf(x,y,z), axis tight
%del2z = 4*del2(z)
%figure; surf(x,y,del2z), axis tight

temp = (Xi.^2).*(Yi.^2);
%temp = Xi.*Yi;
figure('Position',[500 10 512 512]);
subplot(2,1,1);     surfc(Xi,Yi,temp); title 'Potential'; shading (shade); colorbar; rotate3d
Hi = 4*del2(temp);
subplot(2,1,2);     surfc(Xi,Yi,Hi); title 'Hjorth'; shading (shade); colorbar; rotate3d