[FieldTrip] Averaging over frequencies in ft_freqstatistics
Schoffelen, J.M. (Jan Mathijs)
jan.schoffelen at donders.ru.nl
Mon Jul 23 10:58:46 CEST 2018
ft_freqstatistics averages the power across the frequency bins, that have their bin-centre within the range specified by cfg.frequency.
The output frequency in stat.freq represents the average of the bin-centres that went into the computation.
No re-estimation of the power at this frequency is done.
J.M.Schoffelen, MD PhD
Senior Researcher, VIDI-fellow - PI, language in interaction
Physical location: room 00.028
Donders Centre for Cognitive Neuroimaging, Nijmegen, The Netherlands
On 19 Jul 2018, at 09:01, Sebastian Sauppe <sauppe.s at gmail.com<mailto:sauppe.s at gmail.com>> wrote:
Dear FieldTrip list,
I am testing different frequency bands with cluster-based permutation tests using ft_freqstatistics. For this, I use cfg.avgoverfreq = ‚yes‘ when setting up the test. However, I am unsure about how FieldTrip actually handles the frequency averaging. Does it take the mean power of the specified frequencies or does it take the power of the mean frequency?
This is the relevant code I use:
cfg.frequency = [3 8];
cfg.avgoverfreq = 'yes‘;
[stat] = ft_freqstatistics(cfg, data_A, data_B);
In my data, I have the following frequencies: [3.9062 4.8828 6.1035 7.0801 8.0566 9.0332 10.0098]. In the statistics output, after averaging over frequencies stat.freq returns only 6.0059. This is the mean of the frequencies between 3 and 8. But I can’t see whether somehow the power of that frequency was assessed in the test or whether the power of all frequencies in that band was first averaged and then tested.
Dr. Sebastian Sauppe
Department of Comparative Linguistics, University of Zurich
Google Scholar Citations: https://scholar.google.de/citations?user=wEtciKQAAAAJ
ORCID ID: http://orcid.org/0000-0001-8670-8197
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