Note that this reference documentation is identical to the help that is displayed in MATLAB when you type “help ft_redefinetrial”.
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, and require two calls to this function to avoid confucion 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 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 = single number (in unit of time, typically seconds) of the required snippets cfg.overlap = single number (between 0 and 1 (exclusive)) specifying the fraction of overlap between snippets (0 = no overlap) 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. See also FT_DEFINETRIAL, FT_RECODEEVENT, FT_PREPROCESSING