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Bug 667 - error in artifact detection tutorial

Reported 2011-05-13 21:19:00 +0200
Modified 2011-06-06 10:18:48 +0200
Product: FieldTrip
Component: core
Version: unspecified
Hardware: PC
Operating System: Mac OS
Importance: P1 normal
Assigned to: Robert Oostenveld
Depends on:
See also:

Robert Oostenveld - 2011-05-13 21:19:15 +0200

in the tutorial -> artifactdetect >> cfg = ft_artifact_eog(cfg); Warning: multiple versions of SPM on your path will confuse FieldTrip > In fieldtrip\private\warning_once at 75 In ft_defaults at 45 In ft_artifact_eog at 72 Warning: one version of SPM is found here: C:\Program Files\MATLABextern\fieldtrip\external\spm2\spm.m > In ft_defaults at 48 In ft_artifact_eog at 72 Warning: one version of SPM is found here: C:\Program Files\MATLABextern\fieldtrip\external\spm8\spm.m > In ft_defaults at 48 In ft_artifact_eog at 72 getRawCTFBalanceCoefs : Sensor Q11 appears in ds.res4.scrr, but not in ds.res4.chanNames Warning: cannot read balancing coefficients for G3BR > In ft_read_header at 467 In ft_artifact_zvalue at 125 In ft_artifact_eog at 160 searching for artifacts in 1 channels searching trials.poles = 0.9715 + 0.0708i 0.9715 - 0.0708i 1.0012 0.9972 + 0.0075i 0.9972 - 0.0075i 0.9902 0.9390 + 0.0288i 0.9390 - 0.0288i ??? Error using ==> filter_with_correction at 42 Calculated filter coefficients have poles on or outside the unit circle and will not be stable. Try a higher cutoff frequency or a different type/order of filter. Error in ==> ft_preproc_bandpassfilter at 80 filt = filter_with_correction(B,A,dat,dir); Error in ==> preproc at 281 if strcmp(cfg.bpfilter, 'yes'), dat = ft_preproc_bandpassfilter(dat, fsample, cfg.bpfreq, cfg.bpfiltord, cfg.bpfilttype, cfg.bpfiltdir); end Error in ==> ft_artifact_zvalue at 169 dat{trlop} = preproc(dat{trlop},, hdr.Fs, cfg.artfctdef.zvalue, [], fltpadding, fltpadding); Error in ==> ft_artifact_eog at 160 [tmpcfg, artifact] = ft_artifact_zvalue(tmpcfg);

Robert Oostenveld - 2011-05-13 21:39:33 +0200

Maarten was using matlab 2007b,and also reported the problem with ft_artifact_muscle. I can reproduce the problem with ft_artifact_muscle using 2010b, but with the ft_artifact_eog defaults don't see a problem. The error/warning seems to be due to the change in the butter/bandpass filter that Stefan Klanke implemented. What surprises me is that nobody has noticed this before. I have changed the default value for the filter order in the code (and help) from 10 into 8, which should also be steep enough.

Robert Oostenveld - 2011-06-06 10:18:48 +0200

closed several bugs at once