Frequency Analysis!

Muthuraman Muthuraman muthuraman10 at HOTMAIL.COM
Wed Feb 14 18:06:14 CET 2007

Hello ,

Thankyou for the suggestions! I created my own data format and i able to
read in Laplacian transformed data and the result are comparable now

Is there a way to calculate the significance level in fieldtrip for the
coherence calculated, last time i was referred to a Jacknife variance
estimate does it still exist in the fieldtrip coherence analysis, or is
there any other way to calculate the significance level in Fieldtrip

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 data). I
would like to do the Timefrequency analysis for this data and to see the
power for the whole 30 seconds

If i go for 0.5 seconds then i can go only for the time interval of interest

all the other values are above and below this limit are Nan's

I am interested mostly on the lower frequency range from 4 hz to 15 hz, what
would be the right time window if i want to look for the whole 30 seconds of

Thanking you

with regards

>From: Jan Mathijs Schoffelen <Jan.Schoffelen at FCDONDERS.RU.NL>
>Reply-To: FieldTrip discussion list <FIELDTRIP at NIC.SURFNET.NL>
>Subject: Re: [FIELDTRIP] Frequency Analysis!
>Date: Mon, 12 Feb 2007 08:57:28 +0100
>Dear Muthuraman,
>For the mtmwelch-method, the same caveats apply as to the mtmconvol-method.
>If you specify your window to be one second, and your data is also one
>second (perhaps even one sample less? Did you check this, a lonely sample
>easily lost), then there is nothing to welch (because your data can be only
>split up in one overlapping segment of one second, or even cannot be split
>up at all, dependent on your data: see above).
>In the following link you find some info how to create fieldtrippish
>data-objects in matlab:
>You can read in your laplacian transformed data into matlab and create a
>data-structure (some hints are given in the link).
>-----Original Message-----
>From: FieldTrip discussion list [mailto:FIELDTRIP at NIC.SURFNET.NL] On Behalf
>Of Muthuraman Muthuraman
>Sent: Friday, February 09, 2007 1:06 PM
>Subject: [FIELDTRIP] Frequency Analysis!
>Hello ,
>Thankyou JM, for the suggestions regarding the Time-Frequency Analysis, it
>works well now. I need the time information inorder to see what happens to
>the power at a specific time interval.
>>From the previous discussion for the Freqanalysis_mtmwelch method as
>Prof.Robert as suggested i tried to change the frequency resolution to 1 Hz
>in the Mtmwelch method. Now i get all the values to be Nan's.
>cfg.foi        = [2:1:30];
>cfg.t_ftimwin  = ones(1,length(cfg.foi)).*1;
>And also is there way to load the Laplacian transformed data to the
>analysis which is a .mat file and work on it for the coherence analysis. I
>do the laplacian transformation and the welch periodogram method with my
>programs not any software.
>With regards
>Catch all the cricketing action right here. Live score, match reports,
>photos et al.

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