[FieldTrip] Trialwise log of TF transform before condition averaging?

[Hamid Mohseni]

Hi George,

You are right, getting logarithm of the trials and then average
is equivalent to the multiplying trials and then getting log.
It remains that whether summing or multiplying trials can reduce the
outliers.

I therefore really doubt this way of analysis can remove or suppress the
outliers.

Thanks



On 9 March 2013 14:34, George Wallis <wallisgj at gmail.com> wrote:

> Dear fieldtrip experts
>
> When computing condition averages of TF transformed data, I take the log
> of the trialwise data before averaging over the trials for a given
> condition.  As I was taking the log of the trialwise data for trialwise
> analyses, this seemed the most consistent approach. However, I notice it
> isn't implemented in fieldtrip (it requires a tweak of the ft_freqanalysis
> function), and the tf averages tend to look noisier this way than if they
> are averaged before taking the log.
>
> Does anyone have any insight into whether this is a sensible way to
> generate condition averages?  I originally thought this would reduce the
> influence of outlier trials - but since it is equivalent to taking the log
> of the product of all the trials within a condition, perhaps it is going to
> do the opposite?
>
> George
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-- 
Hamid R. Mohseni, PhD
Post-Doctoral Research Assistant
Institute of Biomedical Engineering
University of Oxford, OX3 7DQ, UK
Tel: +44 (0) 1865 2 83826
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