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function [data] = ft_redefinetrial(cfg, data)
% FT_REDEFINETRIAL allows you to adjust the time axis of your data, i.e. to
% change from stimulus-locked to response-locked. Furthermore, it allows
% you to select a time window of interest, or to resegment your long trials
% into shorter fragments.
% Use as
% [data] = ft_redefinetrial(cfg, data)
% where the input data should correspond to the output of FT_PREPROCESSING and the
% configuration should be specified as explained below. Note that some options are
% mutually exclusive. If you want to use both, you neew two calls to this function
% to avoid confusion about the order in which they are applied.
% For selecting a subset of trials you can specify
% cfg.trials = 'all' or a selection given as a 1xN vector (default = 'all')
% For selecting trials with a minimum length you can specify
% cfg.minlength = length in seconds, can be 'maxperlen' (default = [])
% For realiging the time axes of all trials to a new reference time
% point (i.e. change the definition for t=0) you can use the following
% configuration option
% cfg.offset = single number or Nx1 vector, expressed in samples relative to current t=0
% For selecting a specific subsection of (i.e. cut out a time window
% of interest) you can select a time window in seconds that is common
% in all trials
% cfg.toilim = [tmin tmax] to specify a latency window in seconds, can be Nx2 vector
% Alternatively you can specify the begin and end sample in each trial
% cfg.begsample = single number or Nx1 vector, expressed in samples relative to the start of the input trial
% cfg.endsample = single number or Nx1 vector, expressed in samples relative to the start of the input trial
% Alternatively you can specify a new trial definition, expressed in
% samples relative to the original recording
% cfg.trl = Nx3 matrix with the trial definition, see FT_DEFINETRIAL
% Alternatively you can specify the data to be cut into (non-)overlapping
% segments, starting from the beginning of each trial. This may lead to loss
% of data at the end of the trials
% cfg.length = number (in seconds) that specifies the length of the required snippets
% cfg.overlap = number between 0 and 1 (exclusive) specifying the fraction of overlap between snippets (0 = no overlap)
% Alternatively you can merge or stitch pseudo-continuous segmented data back into a
% continuous representation. This requires that the data has a valid sampleinfo field
% and that there are no jumps in the signal in subsequent trials (e.g. due to
% filtering or demeaning). If there are missing segments (e.g. due to artifact
% rejection), the output data will have one trial for each section where the data is
% continuous.
% cfg.continuous = 'yes'
% To facilitate data-handling and distributed computing you can use
% cfg.inputfile = ...
% cfg.outputfile = ...
% If you specify one of these (or both) the input data will be read from a *.mat
% file on disk and/or the output data will be written to a *.mat file. These mat
% files should contain only a single variable, corresponding with the
% input/output structure.
% Copyright (C) 2006-2021, Robert Oostenveld
% This file is part of FieldTrip, see
% for the documentation and details.
% FieldTrip 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 3 of the License, or
% (at your option) any later version.
% FieldTrip is distributed in the hope that it will be useful,
% but WITHOUT ANY WARRANTY; without even the implied warranty of
% GNU General Public License for more details.
% You should have received a copy of the GNU General Public License
% along with FieldTrip. If not, see <>.
% $Id$
% these are used by the ft_preamble/ft_postamble function and scripts
ft_revision = '$Id$';
ft_nargin = nargin;
ft_nargout = nargout;
% do the general setup of the function
ft_preamble init
ft_preamble debug
ft_preamble loadvar data
ft_preamble provenance data
ft_preamble trackconfig
% the ft_abort variable is set to true or false in ft_preamble_init
if ft_abort
% store original datatype
dtype = ft_datatype(data);
% deal with the special case of timelock rpt_chan_time with 1 trial
oneRptTimelock = (strcmp(dtype, 'timelock') && ...
strcmp(data.dimord, 'rpt_chan_time') && ...
size(data.trial, 1) == 1);
% check if the input data is valid for this function, this will convert it to raw if needed
data = ft_checkdata(data, 'datatype', {'raw+comp', 'raw'}, 'feedback', 'yes');
% check if the input cfg is valid for this function
cfg = ft_checkconfig(cfg, 'forbidden', {'trial'}); % prevent accidental typos, see issue 1729
% set the defaults
cfg.offset = ft_getopt(cfg, 'offset', []);
cfg.toilim = ft_getopt(cfg, 'toilim', []);
cfg.begsample = ft_getopt(cfg, 'begsample', []);
cfg.endsample = ft_getopt(cfg, 'endsample', []);
cfg.minlength = ft_getopt(cfg, 'minlength', []);
cfg.trials = ft_getopt(cfg, 'trials', 'all', 1); = ft_getopt(cfg, 'feedback', 'yes');
cfg.trl = ft_getopt(cfg, 'trl', []);
cfg.length = ft_getopt(cfg, 'length', []);
cfg.overlap = ft_getopt(cfg, 'overlap', 0);
cfg.continuous = ft_getopt(cfg, 'continuous', 'no');
% select trials of interest
if ~strcmp(cfg.trials, 'all')
if islogical(cfg.trials)
ft_info('selecting %d trials\n', sum(cfg.trials));
ft_info('selecting %d trials\n', length(cfg.trials));
% select trials of interest
tmpcfg = keepfields(cfg, {'trials', 'showcallinfo', 'trackcallinfo', 'trackconfig', 'trackusage', 'trackdatainfo', 'trackmeminfo', 'tracktimeinfo'});
data = ft_selectdata(tmpcfg, data);
% restore the provenance information
[cfg, data] = rollback_provenance(cfg, data);
if length(cfg.offset)>1 && length(cfg.offset)~=length(cfg.trials)
cfg.offset = cfg.offset(cfg.trials);
if length(cfg.begsample)>1 && length(cfg.begsample)~=length(cfg.trials)
cfg.begsample = cfg.begsample(cfg.trials);
if length(cfg.endsample)>1 && length(cfg.endsample)~=length(cfg.trials)
cfg.endsample = cfg.endsample(cfg.trials);
Ntrial = numel(data.trial);
% check the input arguments, only one method for processing is allowed
numoptions = ~isempty(cfg.toilim) + ~isempty(cfg.offset) + (~isempty(cfg.begsample) || ~isempty(cfg.endsample)) + ~isempty(cfg.trl) + ~isempty(cfg.length) + istrue(cfg.continuous);
if numoptions>1
ft_error('you should specify only one of the options for redefining the data segments');
if numoptions==0 && isempty(cfg.minlength) && strcmp(cfg.trials, 'all')
ft_error('you should specify at least one configuration option');
% start processing
if ~isempty(cfg.toilim)
% select a latency window from each trial
if numel(cfg.toilim) == 2
% specified as single [tstart tend] vector
% expand into Ntrial X 2
cfg.toilim = repmat(cfg.toilim(:)', Ntrial, 1);
begsample = zeros(Ntrial,1);
endsample = zeros(Ntrial,1);
skiptrial = false(Ntrial,1);
for i=1:Ntrial
if cfg.toilim(i,1)>data.time{i}(end) || cfg.toilim(i,2)<data.time{i}(1)
begsample(i) = nan;
endsample(i) = nan;
skiptrial(i) = true;
begsample(i) = nearest(data.time{i}, cfg.toilim(i,1));
endsample(i) = nearest(data.time{i}, cfg.toilim(i,2));
data.trial{i} = data.trial{i}(:, begsample(i):endsample(i));
data.time{i} = data.time{i} ( begsample(i):endsample(i));
% also correct the sample information
if isfield(data, 'sampleinfo')
data.sampleinfo(:, 1) = data.sampleinfo(:, 1) + begsample - 1;
data.sampleinfo(:, 2) = data.sampleinfo(:, 1) + endsample - begsample;
data.time = data.time(~skiptrial);
data.trial = data.trial(~skiptrial);
if isfield(data, 'sampleinfo'), data.sampleinfo = data.sampleinfo(~skiptrial, :); end
if isfield(data, 'trialinfo'), data.trialinfo = data.trialinfo(~skiptrial, :); end
ft_info('removing %d trials in which no data was selected\n', sum(skiptrial));
elseif ~isempty(cfg.offset)
% shift the time axis from each trial
offset = cfg.offset(:);
offset = round(offset); % this is in samples and hence it must be expressed as integers
if length(cfg.offset)==1
offset = repmat(offset, Ntrial, 1);
for i=1:Ntrial
data.time{i} = data.time{i} + offset(i)/data.fsample;
elseif ~isempty(cfg.begsample) || ~isempty(cfg.endsample)
% select a latency window from each trial based on begin and/or end sample
begsample = cfg.begsample(:);
endsample = cfg.endsample(:);
if length(begsample)==1
begsample = repmat(begsample, Ntrial, 1);
if length(endsample)==1
endsample = repmat(endsample, Ntrial, 1);
for i=1:Ntrial
data.trial{i} = data.trial{i}(:, begsample(i):endsample(i));
data.time{i} = data.time{i} ( begsample(i):endsample(i));
% also correct the sampleinfo
if isfield(data, 'sampleinfo')
sampleinfo = data.sampleinfo(:, 1);
data.sampleinfo(:, 1) = sampleinfo(:, 1) + begsample - 1;
data.sampleinfo(:, 2) = sampleinfo(:, 1) + endsample - 1;
elseif ~isempty(cfg.trl)
% select new trials from the existing data
if ischar(cfg.trl)
% load the trial information from file
newtrl = loadvar(cfg.trl, 'trl');
newtrl = cfg.trl;
% ensure that sampleinfo is present, otherwise ft_fetch_data will crash
data = ft_checkdata(data, 'hassampleinfo', 'yes');
% make a copy of the old data
dataold = data;
% make the header
hdr = ft_fetch_header(dataold);
% start with a completely new data structure
data = keepfields(dataold, {'cfg' 'fsample' 'label' 'topo' 'topolabel' 'unmixing' 'mixing' 'grad' 'elec' 'opto'}); % account for all potential fields to be copied over
data.hdr = hdr;
data.trial = cell(1,size(newtrl,1));
data.time = cell(1,size(newtrl,1));
if isfield(dataold, 'trialinfo')
ft_warning('Original data has trialinfo, using user-specified trialinfo instead');
if ~istable(newtrl)
begsample = newtrl(:,1);
endsample = newtrl(:,2);
offset = newtrl(:,3);
begsample = newtrl.begsample;
endsample = newtrl.endsample;
offset = newtrl.offset;
trllength = endsample - begsample + 1;
for iTrl=1:size(newtrl, 1)
data.trial{iTrl} = ft_fetch_data(dataold, 'header', hdr, 'begsample', begsample(iTrl), 'endsample', endsample(iTrl), 'chanindx', 1:hdr.nChans, 'skipcheckdata', 1);
data.time{iTrl} = offset2time(offset(iTrl), dataold.fsample, trllength(iTrl));
% The following ensures correct handling of trialinfo.
% Determine which old trials are present in new trials
iTrlorig = find(begsample(iTrl) <= dataold.sampleinfo(:,2) & endsample(iTrl) >= dataold.sampleinfo(:,1));
if size(newtrl,2)>3 % In case user specified additional trialinfo
data.trialinfo(iTrl,:) = newtrl(iTrl,4:end);
elseif isfield(dataold,'trialinfo') % If old data has trialinfo
if (numel(iTrlorig) == 1 ... % only 1 old trial to copy trialinfo from, or
|| size(unique(dataold.trialinfo(iTrlorig,:),'rows'),1)) ... % all old trialinfo rows are identical
&& ~any(diff(dataold.sampleinfo(:,1))<=0) % and the trials are consecutive segments
data.trialinfo(iTrl,:) = dataold.trialinfo(iTrlorig(1),:);
ft_error('Old trialinfo cannot be combined into new trialinfo, please specify trialinfo in cfg.trl(:,4)');
end % for iTrl
% adjust the sampleinfo in the output
if isfield(dataold, 'sampleinfo')
% adjust the sample information
data.sampleinfo = [begsample endsample];
elseif ~isempty(cfg.length)
% cut the existing trials into segments of the specified length
data = ft_checkdata(data, 'hassampleinfo', 'yes');
% create dummy trl-matrix and recursively call ft_redefinetrial
nsmp = round(cfg.length*data.fsample);
nshift = round((1-cfg.overlap)*nsmp);
newtrl = zeros(0,4);
for k = 1:numel(data.trial)
begsample = data.sampleinfo(k,1);
endsample = data.sampleinfo(k,2);
offset = time2offset(data.time{k}, data.fsample);
thistrl = (begsample:nshift:(endsample+1-nsmp))';
if ~isempty(thistrl) % the trial might be too short
thistrl(:,2) = thistrl(:,1) + nsmp - 1;
thistrl(:,3) = thistrl(:,1) + offset - thistrl(1,1);
thistrl(:,4) = k; % keep the trial number in the 4th column, this is needed further down
newtrl = cat(1, newtrl, thistrl);
clear begsample endsample offset
tmpcfg = keepfields(cfg, {'feedback', 'showcallinfo', 'trackcallinfo', 'trackconfig', 'trackusage', 'trackdatainfo', 'trackmeminfo', 'tracktimeinfo'});
tmpcfg.trl = newtrl;
if isfield(data, 'trialinfo') && ~istable(data.trialinfo)
% replace the trial number with the original trial information
tmpcfg.trl = [newtrl(:,1:3) data.trialinfo(newtrl(:,4),:)];
elseif isfield(data, 'trialinfo') && istable(data.trialinfo)
% construct the trl matrix as a table
begsample = newtrl(:,1);
endsample = newtrl(:,2);
offset = newtrl(:,3);
tmpcfg.trl = [table(begsample, endsample, offset) data.trialinfo(newtrl(:,4),:)];
elseif ~isfield(data, 'trialinfo')
% discard the trial number
tmpcfg.trl = newtrl(:,1:3);
data = removefields(data, {'trialinfo'}); % these are in the additional columns of tmpcfg.trl
data = ft_redefinetrial(tmpcfg, data);
% restore the provenance information
[cfg, data] = rollback_provenance(cfg, data);
elseif istrue(cfg.continuous)
% identify consecutive segments that can be glued back together
data = ft_checkdata(data, 'hassampleinfo', 'yes');
boolvec = artifact2boolvec(data.sampleinfo);
newtrl = boolvec2trl(boolvec);
% In general: An offset of 0 means that the first sample of the trial corresponds
% to the trigger. A positive offset indicates that the first sample is later than
% the trigger.
% here we want to use the start of the recording as t=0
newtrl(:,3) = newtrl(:,1) - 1;
tmpcfg = keepfields(cfg, {'feedback', 'showcallinfo', 'trackcallinfo', 'trackconfig', 'trackusage', 'trackdatainfo', 'trackmeminfo', 'tracktimeinfo'});
tmpcfg.trl = newtrl;
data = removefields(data, {'trialinfo'}); % the trialinfo does not apply any more
data = ft_redefinetrial(tmpcfg, data);
% restore the provenance information
[cfg, data] = rollback_provenance(cfg, data);
end % processing the realignment or data selection
if ~isempty(cfg.minlength)
Ntrial = length(data.trial);
trllength = zeros(Ntrial, 1);
% determine the length of each trial
for i=1:Ntrial
trllength(i) = size(data.trial{i},2) * 1/data.fsample; % this the the DURATION of the selected samples
if ischar(cfg.minlength) && strcmp(cfg.minlength, 'maxperlen')
minlength = max(trllength);
minlength = cfg.minlength;
% remove trials that are too short
skiptrial = (trllength<minlength);
%if ~isempty(trl), trl = trl(~skiptrial,:); end
data.time = data.time(~skiptrial);
data.trial = data.trial(~skiptrial);
if isfield(data, 'sampleinfo'), data.sampleinfo = data.sampleinfo(~skiptrial, :); end
if isfield(data, 'trialinfo'), data.trialinfo = data.trialinfo (~skiptrial, :); end
ft_info('removing %d trials that are too short\n', sum(skiptrial));
% convert back to input type if necessary
switch dtype
case 'timelock'
data = ft_checkdata(data, 'datatype', 'timelock');
if oneRptTimelock
% deal with the special case of rpt_chan_time timelock data with one
% repetition
data.trial = reshape(data.avg, [1 size(data.avg)]);
data.dimord = 'rpt_chan_time';
% keep the output as it is
% do the general cleanup and bookkeeping at the end of the function
ft_postamble debug
ft_postamble trackconfig
ft_postamble previous data
ft_postamble provenance data
ft_postamble history data
ft_postamble savevar data