Time Frequency Analysis!

[Christian Hesse]

Hi Muthuraman,

ok, in that case you can try the following (this assumes you have  
windows of length "winlen" which overlap by "halfwin = winlen/2")

winlen = 0.5;
% this is in seconds you can also use another time window
halfwin = winlen/2;

% the total number of windows covering the 30 second period
nwin = 2.*(30./winlen) - 1;

cfg.method = 'mtmconvol';
cfg.output = 'pow';
cfg.t_ftimwin = ones(1,nwin).*winlen;
cfg.toi = [0:halfwin:30-winlen];

The important things here to check are
1) that cfg.t_ftimwin and cfg.toi contain the same number of elements
2) the times you specify in cfg.toi actually correspond to your time  
axis (i.e. do not start before or go on after).

If you want to use a different overlap, you need to calculate nwin  
slightly differently.

Hope this helps more,
Christian



> Thanks for the suggestion but using the mtmfft which i have done  
> already and it works, my interest now is that i would like to use  
> the Time frequency analysis 'mtmconvol'  to estimate the power in  
> the time frequency scale, in which how to get the whole 30secs  
> continous  data in one time frequency plot(TFR).
>
> Thanking you
>
> with regards
> M.Muthuraman.
>
>> From: Christian Hesse <c.hesse 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: Mon, 19 Feb 2007 11:56:19 +0100
>>
>> Hi Muthuraman,
>>
>>> One more question regarding the Time frequency Analysis, i have  
>>> EMG  data of 24000 data points with a sampling frequeny of 800Hz 
>>> (30  seconds of continous data). I would like to do the  
>>> Timefrequency  analysis for this data and to see the power for  
>>> the whole 30 seconds
>>
>> use preprocessing to get the EMG data into a single 30s trial (if  
>> you  want to analyze the rectified EMG, then do the rectification  
>> in  preprocessing), then use frequanalysis with
>>
>> cfg.method = 'mtmfft';
>> cfg.output = 'pow';
>>
>> this should give you the power spectrum of your EMG data over the   
>> entire 30 second period.
>>
>> Regards,
>> Christian
>>
>>
>> --------------------------------------------------------------------- 
>> -
>> 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: c.hesse at fcdonders.ru.nl
>> Web: www.fcdonders.ru.nl
>> --------------------------------------------------------------------- 
>> -
>>
>>
>>
>>
>
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----------------------------------------------------------------------
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: c.hesse at fcdonders.ru.nl
Web: www.fcdonders.ru.nl
----------------------------------------------------------------------




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