[Mne_analysis] computing head position information
Eric Larson
larson.eric.d at gmail.com
Wed Oct 21 11:53:44 EDT 2020
External Email - Use Caution
>
> I would like to find out if there is a manual or if you could point me to
> literature on the effect of different input parameters in
> mne.chpi.compute_chpi_head_pos ( info, chpi_locs, dist_limit=0.005,
> gof_limit=0.98, adjust_dig=False, verbose=None)
>
These parameters should behave similarly to how they do in MaxFilter's head
position estimation, read more in the MaxFilter manual:
https://ohba-analysis.github.io/osl-docs/downloads/maxfilter_user_guide.pdf
What I am finding is some head position calculations with default goodness
> of fit (0.98) gives me an empty matrix and a “cannot determine the
> transformation” error for all coils. While, if I reduce the goodness of
> fit, or if I set the t_step_max=0.2 (which I am assuming is comparable to
> Maxfilter -movecomp) for calculation of chpi locations (
> mne.chpi.compute_chpi_locs), I do get an head_pos array of a decent size.
>
You might need to set `t_window=0.2` as well. If MaxFilter always outputs
positions separated by 200 ms, then you might also need `t_step_min=0.2` as
well. But there should be some combination of parameters you can use to get
the head positions.
You can also use MaxFilter just for the head position estimation step by
calling it with the `-hp some_filename.pos` option, and then use MNE-Python
to do the movement compensation using these positions computed by MaxFilter.
Eric
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