trigg.m

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function [x,sz] = trigg(s,TRIG,pre,post,gap)
% TRIGG cuts continous sequence into segments.
% Missing values (in case s is to short) are substituted by NaN's.  
%
% [X,sz] = trigg(s, TRIG, PRE, PST [, GAP])
%
% INPUT:
%  S    is the continous data sequence (1 channel per column)
%  TRIG defines the trigger points
%  PRE  offset of the start of each segment (relative to trigger) 
%  PST  offset of the end of each segment (relative to trigger) 
%  GAP  number of NaN's to separate trials (default=0)
%   TRIG, pre, post and gap are counted in samples
%
% OUTPUT:
%  X    is a matrix of size [sz(1), sz(2)*sz(3)]
%  sz   [size(s,2), post-pre+1+gap, length(TRIG)]   
%   sz(1) is the number of channels NS 
%   sz(2) is the number of samples per trial 
%   sz(3) is the number of trials i.e. length(TRIG)
%
% X3D = reshape(X,sz) returns a 3-dimensional matrix 
% X2D = reshape(X(K,:),sz(2:3)) returns channel K in a 2-dimensional matrix 
%
% see also: GETTRIGGER
 
%   $Id: trigg.m 2202 2009-10-27 12:06:45Z schloegl $
%   Copyright (c) 1999-2005 by Alois Schloegl <a.schloegl@ieee.org>
%       This is part of the BIOSIG-toolbox http://biosig.sf.net/
 
 
% This program is free software; you can redistribute it and/or
% modify it under the terms of the GNU General Public License
% as published by the Free Software Foundation; either version 2
% of the  License, or (at your option) any later version.
% 
% This program is distributed in the hope that it will be useful,
% but WITHOUT ANY WARRANTY; without even the implied warranty of
% MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
% GNU General Public License for more details.
% 
% You should have received a copy of the GNU General Public License
% along with this program; if not, write to the Free Software
% Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA  02111-1307, USA.
 
if nargin<5,
    gap = 0;
end;
 
post=round(post);
 
[nr,nc] = size(s);
 
% include leading nan's
off  = min(min([TRIG(:);+Inf])+pre-1,0);
% include following nan's
off2 = max(max([TRIG(:);-Inf])+post-length(s),0);
if ((off~=0) || (off2~=0))
    s    = [repmat(nan,-off,nc);s;repmat(nan,off2,nc)];
    TRIG = TRIG-off;
end; 
 
% devide into segments
N   = post-pre+1+gap;
sz  = [nc, post-pre+1+gap, length(TRIG)];
x   = repmat(NaN, [sz(1), sz(2)*sz(3)]);   
for m = 1:length(TRIG),
    x(:,m*N + (1-N:-gap)) = s(TRIG(m)+(pre:post)',:).';
end;