[Eeglablist] newtimef() with option baseline NaN: What kind of power values?

[Delorme, Arnaud]

Dear Christian,

Yes, you are correct that the values in the ERSP matrix should all be positive. The unit for the values is 10*log(uv^2/Hz).
Since it is log, some values can be negative (log(0.5) -> -0.7). It does not mean that the power is negative though.

Best wishes,

Arno

> On Oct 7, 2019, at 10:11 AM, Delorme, Arnaud <adelorme at ucsd.edu> wrote:
> 
> 
> 
>> On Oct 7, 2019, at 6:32 AM, Christian Scharinger <c.scharinger at gmx.net> wrote:
>> 
>> Dear all,
>> 
>> I am wondering what kind of power values I get out of the newtimef() function when I use it to calculate a time-frequency representation with the option 'baseline', NaN. If I understand the description of the function correctly, whith 'baseline' set to NaN I should get a time-frequency representation with no baseline normalization, i.e., I would expect to get absolute power values out of the function. However, when I look at the values in the ersp matrix there are at the higher frequencies some negative power values. Now I'm a little bit confused because I would expect to have only positive numbers when no baseline normalization is performed? Maybe I missed something?
>> To make it short: What kind of power values does the function newtimef() provide when no baseline is used?
>> 
>> I would be happy to get some clarification on that.
>> 
>> Many thanks in advance,
>> best wishes
>> Christian   
>> 
>> --
>> Dr. Christian Scharinger
>> Multimodal Interaction Lab
>> Leibniz-Institut für Wissensmedien (IWM) /
>> Knowledge Media Research Center Tuebingen
>> Schleichstraße 6 | 72076 Tuebingen
>> 
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>