[FieldTrip] Behavior-power correlations

Arjen Stolk a.stolk8 at gmail.com
Mon May 2 22:41:34 CEST 2016

Hi Kaitlyn,

My question is this: what is the appropriate design array for computing a
> correlation with ft_statfun_correlationT? Is the behavioral variable
> supposed to be part of the design or must it be part of a dummy structure
> designed to be similar in size and structure to the frequency data?

It's really as described on the page you referred to (

n1 = 3;    % n1 is the number of subjects
design(1,1:n1)       = [0.6 0.9 0.1]; %here we insert our independent
variable (behavioral data) in the cfg.design matrix, in this case
reaction times of 3 subjects.

cfg.design           = design;
cfg.ivar             = 1;

stat = ft_freqstatistics(cfg, data_brain{:});

where data_brain is a multiple subjects structure in case you're doing this
at the second/group level (i.e. correlate a behavioral variable to a neural
variable across subjects). Thus, a dummy variable is no longer needed.

Alternatively, is there a way to get, for every individual in the grand
> average, one value representing the average power for, e.g., 300-600ms in
> the 4-7Hz range?

You may want to use ft_freqdescriptives for that, per subject.

Best, Arjen

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