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eeg_time2prev.m
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eeg_time2prev.m
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% EEG_TIME2PREV - returns a vector giving, for each event of specified ("target") type(s),
% the delay (in ms) since the preceding event (if any) of specified
% ("previous") type(s). Requires the EEG.urevent structure, plus
% EEG.EVENT.urevent pointers to it.
%
% NOW SUPERSEDED BY EEG_CONTEXT
% Usage:
% >> [delays,targets,urtargs,urprevs] = eeg_time2prev(EEG,{target},{previous});
% Inputs:
% EEG - structure containing an EEGLAB dataset
% {target} - cell array of strings naming event type(s) of the specified target events
%{previous} - cell array of strings naming event type(s) of the specified previous events
%
% Outputs:
% delays - vector giving, for each event of a type listed in "target", the delay (in ms)
% since the last preceding event of a type listed in "previous" (0 if none such).
% targets - vector of indices of the "target" events in the event structure
% urtargs - vector of indices of the "target" events in the urevent structure
% urprevs - vector of indices of the "previous" events in the urevent structure (0 if none).
%
% Example:
% >> target = {'novel'}; % target event type 'novel'
% >> previous = {'novel', 'rare'}; % either 'novel' or 'rare'
% >> [delays,targets] = eeg_time2prev(EEG,target,previous);
%% Vector 'delays' now contains delays (in ms) from each 'novel' event to the previous
%% 'rare' OR 'novel' event, else 0 if none such. Vector 'targets' now contains the
%% 'novel' event indices.
%%
% Scott Makeig & Arnaud Delorme, SCCN/INC/UCSD, August 28, 2003
% Copyright (C) Scott Makeig & Arnaud Delorme, SCCN/INC/UCSD, August 28, 2003
%
% This file is part of EEGLAB, see http://www.eeglab.org
% for the documentation and details.
%
% Redistribution and use in source and binary forms, with or without
% modification, are permitted provided that the following conditions are met:
%
% 1. Redistributions of source code must retain the above copyright notice,
% this list of conditions and the following disclaimer.
%
% 2. Redistributions in binary form must reproduce the above copyright notice,
% this list of conditions and the following disclaimer in the documentation
% and/or other materials provided with the distribution.
%
% THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
% AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
% IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
% ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE
% LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
% CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
% SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
% INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
% CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
% ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF
% THE POSSIBILITY OF SUCH DAMAGE.
function [delays,targets,urtargets,urprevs] = eeg_time2prev(EEG,target,previous);
verbose = 1; % FLAG (1=on|0=off)
nevents = length(EEG.event);
%
%%%%%%%%%%%%%%%%%%%% Test input arguments %%%%%%%%%%%%%%%%%%%%%%%%%
%
if ~iscell(target)
error('2nd argument "target" must be a {cell array} of event type strings.');
return
end
for k=1:length(target)
if ~ischar([ target{k}{:} ])
error('2nd argument "target" must be a {cell array} of event type strings.');
end
end
if ~iscell(previous)
error('3rd argument "previous" must be a {cell array} of event types.');
return
end
for k=1:length(target) % make all target types strings
if ~ischar(target{k})
target{k} = num2str(target{k});
end
end
for k=1:length(previous) % make all previous types strings
if ~ischar(previous{k})
previous{k} = num2str(previous{k});
end
end
if ~isfield(EEG,'urevent')
error('requires the urevent structure be present.');
return
end
if length(EEG.urevent) < nevents
error('WARNING: In dataset, number of urevents < number of events!?');
return
end
%
%%%%%%%%%%%%%%%%%%%% Initialize output arrays %%%%%%%%%%%%%%%%%%%%%%
%
delays = zeros(1,nevents); % holds output times in ms
targets = zeros(1,nevents); % holds indexes of targets
urtargets = zeros(1,nevents); % holds indexes of targets
urprevs = zeros(1,nevents); % holds indexes of prevs
targetcount = 0; % index of current target
% Below:
% idx = current event index
% uridx = current urevent index
% tidx = target type index
% uidx = previous urevent index
% pidx = previous type index
%
%%%%%%%%%%%for each event in the dataset %%%%%%%%%%%%%%%%%%%%
%
for idx = 1:nevents % for each event in the dataset
%
%%%%%%%%%%%%%%%%%%%%%%%% find target events %%%%%%%%%%%%%%%%%
%
uridx = EEG.event(idx).urevent; % find its urevent index
istarget = 0; % initialize target flag
tidx = 1; % initialize target type index
while ~istarget & tidx<=length(target) % for each potential target type
if strcmpi(num2str(EEG.urevent(uridx).type),target(tidx))
istarget=1; % flag event as target
targetcount = targetcount+1; % increment target count
targets(targetcount) = idx; % save event index
urtargets(targetcount) = uridx; % save urevent index
break % stop target type checking
else
tidx = tidx+1; % else try next target type
end
end
if istarget % if current event is a target type
%
%%%%%%%%%%%%%%%%%%% Find a 'previous' event %%%%%%%%%%%%%%%%%%
%
isprevious = 0; % initialize previous flag
uidx = uridx-1; % begin with the previous urevent
while uridx > 0
pidx = 1; % initialize previous type index
while ~isprevious & pidx<=length(previous) % for each previous event type
if strcmpi(num2str(EEG.urevent(uidx).type),previous(pidx))
isprevious=1; % flag 'previous' event
urprevs(targetcount) = uidx; % mark event as previous
break % stop previous type checking
else
pidx = pidx+1; % try next 'previous' event type
end
end % pidx
if isprevious
break % stop previous event checking
else
uidx = uidx-1; % keep checking for a 'previous' type event
end % isprevious
end % uidx
%
%%% Compute delay from current target to previous event %%%%%
%
if isprevious % if type 'previous' event found
delays(targetcount) = 1000/EEG.srate * ...
(-1)*(EEG.urevent(uridx).latency - EEG.urevent(urprevs(targetcount)).latency);
else
delays(targetcount) = 0; % mark no previous event with 0
end
if verbose
fprintf('%4d. (targ %s) %4d - (prev %s) %4d = %4.1f ms\n',...
targetcount, targets(tidx),idx, ...
previous(pidx),urprevs(targetcount),...
delays(targetcount));
end % verbose
end % istarget
end % event loop
%
%%%%%%%%%%%%%% Truncate the output arrays %%%%%%%%%%%%%%%%%%%%%%
%
if targetcount > 0
targets = targets(1:targetcount);
urtargets = urtargets(1:targetcount);
urprevs = urprevs(1:targetcount);
delays = delays(1:targetcount);
else
if verbose
fprintf('eeg_time2prev(): No target type events found.\n')
end
targets = [];
urtargets = [];
urprevs = [];
delays = [];
end