Hello everyone,

I am trying to calculate the powers of all frequencies (delta, theta, alpha, sigma, beta) during a 3 min. EEG recording with 16 (biosemi16 montage) channels. I want to calculate the average powers of each frequency over the whole recording. MATLAB has a straight-forward function for this:

```
% EEGLAB spectopo function
[spectra,freqs] = spectopo(EEG.data(2,:), 0, EEG.srate, 'nfft', 1024); %
For channel 2 (C4)
thetaIdx = find(freqs>=4 & freqs<=8); % theta=4-8
thetaPower = 10^(mean(spectra(thetaIdx))/10); % mean theta
power
alphaIdx = find(freqs>=8 & freqs<=12); % alpha=8-12
alphaPower = 10^(mean(spectra(alphaIdx))/10); % mean alpha
power
eeglabThetaAlphaRatio = thetaPower/alphaPower;
figure; subplot(1,2,1); plot(freqs,10.^(spectra/10))
% Matlab pwelch function
x = EEG.data(2, :); % For channel 2 (C4)
Fs = EEG.srate; % Sampling frequency
L = EEG.pnts; % Length of signal
NFFT = 2^nextpow2(L); % Next power of 2 from length of x
% X = fft(x,NFFT)/L;
% freqs = Fs/2*linspace(0,1,NFFT/2+1);
% spectra = abs(X(1:NFFT/2+1));
NOVERLAP = 0;
WINDOW = 512;
[spectra,freqs] = pwelch(x,WINDOW,NOVERLAP,NFFT,EEG.srate);
thetaIdx = find(freqs>=4 & freqs<=8); % theta=4-8
thetaPower = mean(spectra(thetaIdx)); % mean theta power
alphaIdx = find(freqs>=8 & freqs<=12); % alpha=8-12
alphaPower = mean(spectra(alphaIdx)); % mean alpha power
matlabThetaAlphaRatio = thetaPower/alphaPower;
```

But I want to achieve a similar output but then with MNE. I tried this function to do so:

```
def eeg_power_band(epochs):
# specific frequency bands
FREQ_BANDS = {"delta": [0.5, 4.5],
"theta": [4.5, 8.5],
"alpha": [8.5, 11.5],
"sigma": [11.5, 15.5],
"beta": [15.5, 30]}
psds, freqs = psd_welch(epochs, picks='eeg', fmin=0.5, fmax=30.)
# Normalize the PSDs
psds /= np.sum(psds, axis=-1, keepdims=True)
X = []
for fmin, fmax in FREQ_BANDS.values():
psds_band = psds[:, :, (freqs >= fmin) & (freqs < fmax)].mean(axis=-1)
X.append(psds_band.reshape(len(psds), -1))
return np.concatenate(X, axis=1)
```

But itâ€™s not working because I am not working with epochs and I want to calculate the power of all frequencies over all channels and not just one signal. Is that possible to do in MNE?

Thank you for your help!

Kind regards,

Laura