tfanalysis - NaN
Virginie van Wassenhove
vvw at CALTECH.EDU
Mon Jun 25 19:38:38 CEST 2007
Hi Christian,
thanks for your inputs. Actually, I have tried different window sizes
and frequency parameters (and wavelet, tf tiling,...). I would not
expect to obtain NaN for a narrow band in higher frequencies (say
35-45Hz) with 2Hz and 4 cycles resolution with the same epoch but I still do.
I'll try with a longer epoch, but I find puzzling that I should still
get NaN when the resolution should be sufficient for the computations.
Cheers,
Virgine
At 01:19 AM 6/25/2007, Christian Hesse wrote:
>Hi Virginie,
>
>the function freqanalysis will return NaNs when a time frequency
>tile extends beyond a corresponding data segment. One would usually
>expect a "U" shaped padding of NaNs at the boundaries of any TFR
>which has longer time windows for lower frequencies. From the cfg
>options you specify below I can see that you have a data segment of
>1.1 seconds length and the moving windows cfg.t_tfimwin are quite
>long at the low ffrequencies, e.g., 1 Hz = 4 s, 6 Hz = 0.6666 s.
>Hence the NaNs seem perfectly "normal" in this case. The only way to
>avoid NaN in the time window of interest (using this type of
>time-frequency tiling) is to make your epochs longer.
>
>Hope this helps,
>Christian
>
>
>On 21 Jun 2007, at 20:44, Virginie van Wassenhove wrote:
>
>>Hello again.
>>
>>I am finding NaN whatever method I use (multitaper and wavelet
>>analysis), yet using a different analysis tool with similar
>>parameters I obtain clean results.
>>epoch length = 1.1 s
>>baseline length = 0.3 s
>>sampling rate = 500Hz
>>
>>I tried several suggestions listed in the previous message list for
>>a similar problem, but none seem to provide reasonable results (aka
>>always NaN).
>>Also tried with different subjects, no particular error otherwise.
>>I am sending a sample script in case someone has a suggestion on this...
>>Thanks for your help once more!
>>
>>Virginie
>>
>>%% ================================================
>>% TF analysis - MULTITAPER
>>cfg = [];
>>cfg.method = 'mtmconvol';
>>cfg.taper = 'hanning';
>>cfg.output = 'powandcsd';
>>%cfg.channel = 'all';
>>cfg.channel = 'E75';
>>
>>%win_length = 0.128;
>>%win_n = floor(2.*(1.1./win_length)-1);
>>
>>cfg.foi = 1:5:45;
>>%cfg.t_ftimwin = ones(1,win_n).*win_length;
>>cfg.t_ftimwin = 4./cfg.foi;
>>%cfg.toi = -0.3:win_length/2:0.8;
>>cfg.toi = -0.3:0.05:0.8;
>>
>>% cfg.pad = 'maxperlen';
>>% cfg.keeptrials = 'no';
>>% cfg.keeptapers ='no';
>>s08_ill_mult = freqanalysis(cfg,s08_ill);
>>
>>%% ========================
>>% plot freq data
>>cfg = [];
>>cfg.baseline = [-0.3 0];
>>cfg.layout = egilay;
>>cfg.zlim = [-0.00001 0.000001]; % a comparer entre
>>participants
>>% warning off % NaN
>>clf
>>%multiplotTFR(cfg,s08_ill_mult);
>>singleplotTFR(cfg,s08_ill_mult);
>>
>>%% ================================================
>>% TF analysis - wavelet
>>cfg = [];
>>cfg.method = 'wltconvol';
>>cfg.width = 4;
>>cfg.output = 'pow';
>>cfg.foi = 1:2:30;
>>cfg.toi = -0.3:0.05:0.8;
>>s14_ill_wvlt = freqanalysis(cfg, s14_ill);
>>%% ========================
>>cfg = [];
>>cfg.baseline = [-0.3 0];
>>cfg.zlim = [-1 1];
>>cfg.showlabels = 'yes';
>>cfg.layout = egilay;
>>clf
>>multiplotTFR(cfg, s14_ill_wvlt)
>>
>>%% ================================================
>>
>>
>>
>>
>>
>>
>>Virginie van Wassenhove, PhD
>>
>>:::::::::::: contact info :::::::::::::
>>Caltech - Division of Biology
>>1200 E. California Blvd M/C 139-74
>>Pasadena CA 91125 USA
>>:::::::::::::::::::::::::::::::::::::::::::::::::
>><mailto:vvw at caltech.edu>vvw at caltech.edu
>><mailto:Virginie.van.Wassenhove at gmail.com>Virginie.van.Wassenhove at gmail.com
>>W: 626.395.8959
>><http://www.its.caltech.edu/~vvw>http://www.its.caltech.edu/~vvw
>>
>>:::::::::::::::::: extras ::::::::::::::::::::
>><http://www.kiva.org>http://www.kiva.org
>>http://www.thehungersite.com/
>><http://www.agloco.com/r/BBBS1539>http://www.agloco.com/r/BBBS1539
>>:::::::::::::::::::::::::::::::::::::::::::::::::
>>
>>----------------------------------
>>The aim of this list is to facilitate the discussion between users
>>of the FieldTrip toolbox, to share experiences and to discuss new
>>ideas for MEG and EEG analysis. See also
>><http://listserv.surfnet.nl/archives/fieldtrip.html>http://listserv.surfnet.nl/archives/fieldtrip.html
>>and <http://www.ru.nl/fcdonders/fieldtrip>http://www.ru.nl/fcdonders/fieldtrip.
>
>----------------------------------------------------------------------
>Christian Hesse, PhD, MIEEE
>
>F.C. Donders Centre for Cognitive Neuroimaging
>P.O. Box 9101
>NL-6500 HB Nijmegen
>The Netherlands
>
>Tel.: +31 (0)24 36 68293
>Fax: +31 (0)24 36 10989
>
>Email: <mailto:c.hesse at fcdonders.ru.nl>c.hesse at fcdonders.ru.nl
>Web: <http://www.fcdonders.ru.nl>www.fcdonders.ru.nl
>----------------------------------------------------------------------
>
>
>
>
>----------------------------------
>
>The aim of this list is to facilitate the discussion between users
>of the FieldTrip toolbox, to share experiences and to discuss new
>ideas for MEG and EEG analysis.
>
>http://listserv.surfnet.nl/archives/fieldtrip.html
>
>http://www.ru.nl/fcdonders/fieldtrip/
Virginie van Wassenhove, PhD
:::::::::::: contact info :::::::::::::
Caltech - Division of Biology
1200 E. California Blvd M/C 139-74
Pasadena CA 91125 USA
:::::::::::::::::::::::::::::::::::::::::::::::::
vvw at caltech.edu
Virginie.van.Wassenhove at gmail.com
W: 626.395.8959
http://www.its.caltech.edu/~vvw
:::::::::::::::::: extras ::::::::::::::::::::
http://www.kiva.org
http://www.thehungersite.com/
http://www.agloco.com/r/BBBS1539
:::::::::::::::::::::::::::::::::::::::::::::::::
----------------------------------
The aim of this list is to facilitate the discussion between users of the FieldTrip toolbox, to share experiences and to discuss new ideas for MEG and EEG analysis. See also http://listserv.surfnet.nl/archives/fieldtrip.html and http://www.ru.nl/fcdonders/fieldtrip.
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