[Eeglablist] (no subject)

[Arnaud Delorme]

>
> E.g. given a 1.5sec eopoch at 250 Hz sampling rate, pop_timef() runs a 
> 256 ms / 64 samples running window FFT with a padratio of 4 and plots 
> 50 frequencies from 1.0 - 49.2 Hz:
> Firstly, is a padratio of 4 appropriate?


The 'padratio' determines the number of 0 added at the end of the FFT. 
This padding is used to smooth the spectral decomposition. However, all 
that's going on with zero-padded FFT's is a  resampling of the same 
spectrum. So your  FFT  output will have more data points;  but the  
extra points are just interpolated information.

> Secondly, what I don`t understand from the tutorial/help is, if I have 
> to re-scale the range of output-frequencies of pop_timef() in the 
> 'freqs'- file according to the padratio in order to represent them 
> correctly in tftopo()?

No you don't. The number of frequencies returned by the timef() function 
depends on the 'padratio' value you used. You should consider 'padratio' 
= "artificially add extra frequencies to smooth the visual output".

Best

Arno

>  
> Thanks for any help!
>  
> Best Regards,
> Tom
>  
>  
>  
> Tom Eichele, PhD Student
> Department of Medical and Biological Psychology
> Section for Cognitive Neurosciences
> University of Bergen
> Tom.Eichele at psybp.uib.no <mailto:Tom.Eichele at psybp.uib.no>
> phones:
> +47-55586290 (office)
> +47-55586201 (lab)



-- 

*Arnaud Delorme, Ph.D.*
Computational Neurobiology Lab, Salk Institute
10010 North Torrey Pines Road
La Jolla, CA 92037 USA

*Tel* : /(+1)-858-458-1927 ext 15/
*Fax* : /(+1)-858-458-1847/
*Web page *: www.sccn.ucsd.edu/~arno <http://www.sccn.ucsd.edu/%7Earno>


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