[Eeglablist] Problem with base line in time-frequency

[Brian Roach]

In addition to what has already been covered, you should know that you will 
need longer epochs to use -1000 to -500ms as your baseline.  Depending on 
what you decide to examine as the lowest frequency, that will determine the 
necessary epoch length.  From the -126 to 1200ms window you describe, I 
believe you need to have epochs starting around -2000 or -1900
At 07:25 AM 8/7/2007, Arnaud Delorme wrote:

> > I have epoched my data from -1000 ms to +2000ms in order to have a very
> > large one.
> > When I apply the time frequency function (study, compute ERSP), I obtain
> > a time freq representation from -126ms to 1200ms maxi.
> >
> > Why?
> >
>
>This is because the time-frequency decomposition trim the time window.
>If your lower frequency is 3 Hz and you have a 3-cycle wavelet (at 3
>Hertz) for instance, this wavelet duration is 1000 ms (1 s). This means
>that 500 ms will be trimmed on each side.
>
> > Now i would like to do different ERSP. I would like that the [-1000,
> > -500] period to be my baseline. And then have a representation from -500
> > to +1500.  Is it possible? I have tried with the option 'baseline' in
> > the ERSP box but EEGlab give me error message.
> >
>
>The baseline cannot be entered yet through this interface but we have
>entered an bug repport for enhancement so this should be possible soon.
>
>Best regards,
>
>Arno
>
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