[Eeglablist] Enquiry regarding power values calculated using spectopo

[#HENG JIAMIN GLADYS#]

Dear EEGlab list,

I have calculated power values using the following formula, as found in a previous post (https://sccn.ucsd.edu/pipermail/eeglablist/2015/009249.html):

% for your epoched data, channel 2
[spectra,freqs] = spectopo(EEG.data(2,:,:), 0, EEG.srate);

% delta=1-4, theta=4-8, alpha=8-13, beta=13-30, gamma=30-80
deltaIdx = find(freqs>1 & freqs<4);
thetaIdx = find(freqs>4 & freqs<8);
alphaIdx = find(freqs>8 & freqs<13);
betaIdx  = find(freqs>13 & freqs<30);
gammaIdx = find(freqs>30 & freqs<80);

% compute absolute power
deltaPower = mean(10.^(spectra(deltaIdx)/10));
thetaPower = mean(10.^(spectra(thetaIdx)/10));
alphaPower = mean(10.^(spectra(alphaIdx)/10));
betaPower  = mean(10.^(spectra(betaIdx)/10));
gammaPower = mean(10.^(spectra(gammaIdx)/10));

>From my understanding, spectopo "plots the mean log spectrum of a set of data epochs at all channels as a bundle of traces".
Therefore, the spectra output is mean log values.
With the formula to compute absolute by taking 10.^(spectra(freqIdx)/10), does that mean that the power value is transformed back to actual raw values?

I'm asking this as my resulting data appear to be mostly positively skewed, and I am planning to do a log10 transformation, but am not sure if I am applying log transformation twice on the data.

Thanks in advance,
Gladys