# [Eeglablist] newtimef window length

Makoto Miyakoshi mmiyakoshi at ucsd.edu
Thu Jan 12 22:16:42 PST 2017

```Dear Cigir,

For your info, this is the timely updated wiki.
https://sccn.ucsd.edu/wiki/Makoto%27s_preprocessing_pipeline#A_tip_to_compute_time-frequency_transform_.28i.e._ERSP_.26_ITC.29_.2801.2F11.2F2017_updated.29

Where does that extra 113.28 ms come from? newtimef() calls dftfilt3()
function to define Morlet waveform as a mother wavelet, which has
distribution in both time and frequency. So 3Hz you specify is not exactly
3Hz after letting it have frequncy distribution, which is why it becomes a
little bit longer... that's my 'guess'. I mean, it would be tautologically
obvious to watch how dftfilt3() creates the wavelet by using debug mode.
There is no mistery, the textbook equation is written in that code (by Ray
Ramirez, I met him in SCCN.)

>From Lufthansa455 to Frankfurt,

Makoto

On Thu, Jan 5, 2017 at 1:44 AM, Cigir Kalfaoglu <cigirkalfaoglu at gmail.com>
wrote:

> Hello,
> It probably has an easy answer but here is my question:
> When I apply the newtimef function with varwin [3 0], the wavelet used
> should contain 3 cycles in all frequencies applied. I am interested in
> extracting spectral power in 3Hz oscillations. So I use the below code:
>
> [ersp_full, itc, powbase, times] = newtimef(data, ...
>     length(data), ...
>     [-5000 1000], ... % Yes, I have an epoch length of 6 seconds.
>     256, ...
>     varwin, [3 0], ...
>     'freqs',3,...
>     'baseline',[-5000 -200],...
>     'timesout',-1);
>
> The sliding window size is returned as 1113.28ms. However, 3 complete
> cycles of a 3Hz wave spans (3cycles * 1000ms / 3cycles = ) 1000ms.
> I can't seem to figure out where then the extra 113.28ms comes from.
> Can some one please point me in the right direction for the answer?
>
> C
>
>
>
>
>
>
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--
Makoto Miyakoshi
Swartz Center for Computational Neuroscience
Institute for Neural Computation, University of California San Diego
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