# [FieldTrip] How can I calculate phase locking factor in FieldTrip?

"Jörn M. Horschig" jm.horschig at donders.ru.nl
Fri Jan 13 10:48:56 CET 2012

```Dear Shogo,

As far as I know, there is no built-in function to compute a
phase-locking factor in FieldTrip, so I am afraid that you have to
program this on your own. However, all values you need can be collected
in FieldTrip. You can either apply a Hilbert transform on your data to
obtain instanenous phase (set cfg.hilbert='yes' prior to calling
/ft_preprocessing/) or get the phase information out from the
fourierspectrum (cfg.output='fourier' prior to calling
/ft_freqanalysis/). In both case, you should be able to get the phase
out by calling the Matlab built-in function /angle()/. Computing the PLF
should then be rather straight-forward.

Also, maybe this can be of help:
http://en.wikipedia.org/wiki/Von_Mises_distribution

Hope this helps! Best,
Jörn

On 1/13/2012 2:49 AM, ?? ?? wrote:
> Hi everyone!
>
> I'm a FieldTrip beginner and I have a question.
> I'm sure I can estimate time frequency power with FieldTrip.
> But I don't know how I can estimate time-frequency phase locking factor.
> phase locking factor is defined as following equation.
> Phase-locking(t)=1/N x |?z(t)|, where N is the number of epochs and z(t) refers to the continuous phase of a single trial.
> Here, z is a complex value on the unit circle, i.e., z=exp(jq), where q is the phase of an oscillation and j is the imaginary unit (e.g. Tallon-baudry et al., 1996).
> Does anyone know how to calculate this phase locking factor with FieldTrip?
> Any answer will help me.
>
> Best regards,
>
> Shogo Hirano
>
> Department of Neuropsychiatry
> Graduate school of medical sciences
> Kyushu University
> Fukuoka, Japan
>
>
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> fieldtrip mailing list
> fieldtrip at donders.ru.nl
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--
Jörn M. Horschig
PhD Student
Donders Institute for Brain, Cognition and Behaviour
Centre for Cognitive Neuroimaging
Neuronal Oscillations Group

P.O. Box 9101
NL-6500 HB Nijmegen
The Netherlands

Contact:
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