Time frequency Analysis!

[Jan Mathijs Schoffelen]

Dear Muthuraman,

In your last mail you wrote:
>I do get any warning while executing the singleplotTFR function
Does this mean that you do, or do not get any warnings?

>cfg.ouput='powandcsd';
Please note that it should read cfg.ouTput (without the capital letter T)


>cfg.baselinetype=[0.1 1.0];
This is obviously wrong: cfg.baselinetype specifies how to do baseline
correction. This can be 'relative' 'absolute' or 'relchange'. Please consult
the help of this function, or of freqbaseline.m
You specify the baseline-interval with cfg.baseline.

>cfg.zlim=[-2e-27 2e-27];
Your values seem to be completely clipped. Did you try around with different
zlims? A typical value of 2e-27 applies to MEG, when no relative or
relchange baselining is involved. EEG is measured in mV's, and power is
measured in mV's-squared, so something in the order of 2e-6 seems more
appropriate to me.

Note that the nans arise when there is not sufficient data in the timewindow
outside [0.25 0.75]. This of course is due to the fact that your data is
only defined between [0 1], and your timewindow for the time-frequency
analysis is 0.5 seconds.

Yours,

Jan-Mathijs




>From: Jan Mathijs Schoffelen <Jan.Schoffelen at FCDONDERS.RU.NL>
>Reply-To: FieldTrip discussion list <FIELDTRIP at NIC.SURFNET.NL>
>To: FIELDTRIP at NIC.SURFNET.NL
>Subject: Re: [FIELDTRIP] Time frequency Analysis!
>Date: Tue, 30 Jan 2007 17:34:44 +0100
>
>Dear Muthuraman,
>
>It pleases us that we finally got you to try multi-tapers for your spectral
>analysis! Sometimes it's hard convincing people, but in the end...
>
>First of all there's a typo in your configuration for the frequency
>analysis; this does not explain your results, but as an extra service to
>you
>I'd like to point it out. You specify cfg.ouput, where I guess you mean
>cfg.output. Moreover, since you have an EMG-channel in your data, you might
>be interested in computing the coherence, but therefore you have to specify
>cfg.output = 'powandcsd'.
>
>Regarding your nans: did you check whether there are any numbers in
>TFRmult.powspctrm. If this is the case, your problem most likely arises in
>the plotting. You specify cfg.baselinetype = 'relative', but you do not
>specify the baseline-interval. Do you get a warning when executing the
>singleplotTFR-function?
>If there are only nans in your TFRmult, then I don't get it, because your
>configuration looks OK to me?
>
>By the way, which version of fieldtrip are you using? If you are using an
>old one, it might be worthwile to download the latest version (there's a
>daily update on the FTP-server, you can get there through the
>fieldtrip-website), and try the script again (with the small changes
>suggested).
>
>Yours,
>
>Jan-Mathijs
>
>
>-----Original Message-----
>From: FieldTrip discussion list [mailto:FIELDTRIP at NIC.SURFNET.NL] On Behalf
>Of Muthuraman Muthuraman
>Sent: Tuesday, January 30, 2007 3:40 PM
>To: FIELDTRIP at NIC.SURFNET.NL
>Subject: [FIELDTRIP] Time frequency Analysis!
>
>Hello Fieldtrippers,
>
>I have question regarding the Time-Frequency analysis using tapers,
>'mtmconvol' or time frequency analysis using wavelets 'wltconvol'
>these are the parameters i use, i get all the values to be Nan's
>Is there something wrong which i need to change in the parameters for the
>timefrequency analysis
>
>hdr     = read_fcdc_header('pd_mof_tr0_c_0306.cnt');
>emgindx = strmatch('M', hdr.label);
>rstindx = setdiff(1:length(hdr.label),emgindx);
>
>trl = [];
>trl(:,1) = [21:1000:74520-1000]';
>trl(:,2) = [1020:1000:74520]';
>trl(:,3) = 0;
>
>
>cfg.dataset = 'pd_mof_tr0_c_0306.cnt';
>cfg.trl     = trl;
>cfg.channel = hdr.label(rstindx);
>cfg.blc     = 'yes';
>data        = preprocessing(cfg);
>
>cfg.channel  = hdr.label(emgindx);
>cfg.hpfilter = 'yes';
>cfg.hpfreq   = 10;
>cfg.rectify  = 'yes';
>emg          = preprocessing(cfg);
>
>for j = 1:length(emg.trial)
>   emg.trial{j} = blc(emg.trial{j});
>end
>data         = appenddata([],data,emg);
>
>%---freqanalysis-mtmconvol
>cfg=[];
>cfg.ouput='pow';
>cfg.sgn='data';
>cfg.method='mtmconvol';
>cfg.channel    = channelselection({'all' 'M1'}, data.label);
>cfg.foi=2:2:30;
>numfoi=length(cfg.foi);
>cfg.t_ftimwin=zeros(1,numfoi);
>cfg.t_ftimwin(:)=0.5;
>cfg.tapsmofrq=zeros(1,numfoi);
>cfg.tapsmofrq(:)=10;
>cfg.toi=-0.5:0.05:1.0;
>cfg.taper='dpss';
>cfg.pad=2;
>cfg.keeptrials='no';
>TFRmult=freqanalysis(cfg,data);
>
>%---Plotting
>cfg=[];
>cfg.baselinetype='relative';
>cfg.zlim=[-2e-27 2e-27];
>cfg.showlabels='yes';
>cfg.channel='C3';
>singleplotTFR(cfg,TFRmult);
>
>
>Thanking you
>
>With regards
>M.Muthuraman.
>
>_________________________________________________________________
>Tickle your funny bone with Rahul Phondke
>http://content.msn.co.in/Lifestyle/Moreonlifestyle/LifestyleFB_101106_1455.
h
>tm

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