FT_ARTIFACT_ZVALUE
Note that this reference documentation is identical to the help that is displayed in MATLAB when you type “help ft_artifact_zvalue”.
FT_ARTIFACT_ZVALUE reads the interesting segments of data from file and identifies artifacts by means of thresholding the z-transformed value of the preprocessed raw data. Depending on the preprocessing options, this method will be sensitive to EOG, muscle or jump artifacts. This procedure only works on continuously recorded data. Use as [cfg, artifact] = ft_artifact_zvalue(cfg) with the configuration options cfg.dataset = string with the filename or cfg.headerfile = string with the filename cfg.datafile = string with the filename and optionally cfg.headerformat cfg.dataformat Alternatively you can use it as [cfg, artifact] = ft_artifact_zvalue(cfg, data) where the input data is a structure as obtained from FT_PREPROCESSING. The required configuration settings are: cfg.trl = structure that defines the data segments of interest. See FT_DEFINETRIAL cfg.continuous = 'yes' or 'no' whether the file contains continuous data (default = 'yes') and cfg.artfctdef.zvalue.channel cfg.artfctdef.zvalue.cutoff cfg.artfctdef.zvalue.trlpadding cfg.artfctdef.zvalue.fltpadding cfg.artfctdef.zvalue.artpadding If you encounter difficulties with memory usage, you can use cfg.memory = 'low' or 'high', whether to be memory or computationally efficient, respectively (default = 'high') The optional configuration settings (see below) are: cfg.artfctdef.zvalue.artfctpeak = 'yes' or 'no' cfg.artfctdef.zvalue.interactive = 'yes' or 'no' If you specify artfctpeak='yes', the maximum value of the artifact within its range will be found and saved into cfg.artfctdef.zvalue.peaks. If you specify interactive='yes', a GUI will be started and you can manually accept/reject detected artifacts, and/or change the threshold. To control the graphical interface via keyboard, use the following keys: q : Stop comma : Step to the previous artifact trial a : Specify artifact trial to display period : Step to the next artifact trial x : Step 10 trials back leftarrow : Step to the previous trial t : Specify trial to display rightarrow : Step to the next trial c : Step 10 trials forward k : Keep trial space : Mark complete trial as artifact r : Mark part of trial as artifact downarrow : Shift the z-threshold down z : Specify the z-threshold uparrow : Shift the z-threshold down Use also, e.g. as input to DSS option of ft_componentanalysis cfg.artfctdef.zvalue.artfctpeakrange=[-0.25 0.25], for example to indicate range around peak to include, saved into cfg.artfctdef.zvalue.dssartifact. The default is [0 0]. Range will respect trial boundaries (i.e. be shorter if peak is near beginning or end of trial). Samples between trials will be removed; thus this won't match .sampleinfo of the data structure. Configuration settings related to the preprocessing of the data are cfg.artfctdef.zvalue.lpfilter = 'no' or 'yes' lowpass filter cfg.artfctdef.zvalue.hpfilter = 'no' or 'yes' highpass filter cfg.artfctdef.zvalue.bpfilter = 'no' or 'yes' bandpass filter cfg.artfctdef.zvalue.bsfilter = 'no' or 'yes' bandstop filter for line noise removal cfg.artfctdef.zvalue.dftfilter = 'no' or 'yes' line noise removal using discrete fourier transform cfg.artfctdef.zvalue.medianfilter = 'no' or 'yes' jump preserving median filter cfg.artfctdef.zvalue.lpfreq = lowpass frequency in Hz cfg.artfctdef.zvalue.hpfreq = highpass frequency in Hz cfg.artfctdef.zvalue.bpfreq = bandpass frequency range, specified as [low high] in Hz cfg.artfctdef.zvalue.bsfreq = bandstop frequency range, specified as [low high] in Hz cfg.artfctdef.zvalue.lpfiltord = lowpass filter order cfg.artfctdef.zvalue.hpfiltord = highpass filter order cfg.artfctdef.zvalue.bpfiltord = bandpass filter order cfg.artfctdef.zvalue.bsfiltord = bandstop filter order cfg.artfctdef.zvalue.medianfiltord = length of median filter cfg.artfctdef.zvalue.lpfilttype = digital filter type, 'but' (default) or 'firws' or 'fir' or 'firls' cfg.artfctdef.zvalue.hpfilttype = digital filter type, 'but' (default) or 'firws' or 'fir' or 'firls' cfg.artfctdef.zvalue.bpfilttype = digital filter type, 'but' (default) or 'firws' or 'fir' or 'firls' cfg.artfctdef.zvalue.bsfilttype = digital filter type, 'but' (default) or 'firws' or 'fir' or 'firls' cfg.artfctdef.zvalue.detrend = 'no' or 'yes' cfg.artfctdef.zvalue.demean = 'no' or 'yes' cfg.artfctdef.zvalue.baselinewindow = [begin end] in seconds, the default is the complete trial cfg.artfctdef.zvalue.hilbert = 'no' or 'yes' cfg.artfctdef.zvalue.rectify = 'no' or 'yes' The output argument "artifact" is a Nx2 matrix comparable to the "trl" matrix of FT_DEFINETRIAL. The first column of which specifying the beginsamples of an artifact period, the second column contains the endsamples of the artifactperiods. See also FT_REJECTARTIFACT, FT_ARTIFACT_CLIP, FT_ARTIFACT_ECG, FT_ARTIFACT_EOG, FT_ARTIFACT_JUMP, FT_ARTIFACT_MUSCLE, FT_ARTIFACT_THRESHOLD, FT_ARTIFACT_ZVALUE