[FieldTrip] Outputting average power with ft_freqanalysis

[Schoffelen, J.M. (Jan Mathijs)]

Dear Lizzie,

You haven’t done anything wrong, and the output is exactly as expected. You almost solved it yourself, since indeed you would want to need the option cfg.avgoverfreq = ‘yes’, but this should be invoked in another function:

cfg = [];
cfg.avgoverfreq = ‘yes’;
FFThann = ft_freqanalysis(cfg, FFThann);

Best wishes,

Jan-Mathijs


On 06 Oct 2016, at 16:03, Shephard, Elizabeth <elizabeth.1.shephard at kcl.ac.uk<mailto:elizabeth.1.shephard at kcl.ac.uk>> wrote:

Dear all

I am fairly new to FieldTrip so apologies if this is a very basic question...

I am using ft_freqanalysis and wanted to obtain average power values in frequency bands rather than power values at particular frequencies. So, following the documentation online, I specified the following:


cfg = [];
cfg.method = 'mtmfft';
cfg.taper = 'hanning';
cfg.foilim = [1 3];        % get power in delta range
cfg.keeptrials = 'yes';
cfg.output = 'pow';
FFThann = ft_freqanalysis(cfg, data);

But the powspctrm field I get in FFThann gives power values for 0.5 Hz steps across the 1-3 Hz range, rather than a single average power value for the 1-3 Hz range.

I was wondering if I have specified something incorrectly? I've also tried adding "cfg.avgoverfreq = 'yes';" but this doesn't change the output.

Many thanks in advance
Lizzie


---------------------------------------------------------------------------
Lizzie Shephard, PhD
Postdoctoral researcher
2.21 MRC SGDP Centre
Institute of Psychiatry, Psychology, & Neuroscience
King’s College London
De Crespigny Park
London, SE5 8AF
0207 848 5272
elizabeth.1.shephard at kcl.ac.uk<mailto:elizabeth.1.shephard at kcl.ac.uk>


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