[Mne_analysis] Maxfilter error: ill conditioned matrix

Eric Larson larson.eric.d at gmail.com
Wed Apr 18 12:44:00 EDT 2018
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Hey Sophie,

What is the head position change/distance (`destination` and the
`info['dev_head_t']['trans'][:3, 3])?

Are you using regularization? Time-varying head positions (head_pos is not
None)?

The "bad condition" suggests that something might be amiss, and if nothing
is, that the resulting data reconstruction could amplify noise. Usually
using regularization prevents this problem, though.

Eric


On Wed, Apr 18, 2018 at 9:32 AM, Sophie Herbst <ksherbst at googlemail.com>
wrote:

> Dear all,
> I am using maxfilter from within mne_python, and I am getting the
> following error for several participants:
> Matrix is badly conditioned: 22221 >= 1000
> Head position change is over 25mm
>
> At first I thought it was because the HPI wasn't fit properly (I had one
> participant for whom 2/4 coils had a too large distance), but I am also
> getting the matrix-badly-condition error with other participants for whom
> the HPI was fine.
>
> I know that I can set the function to give a warning instead of an error,
> but I still would like to understand what happens.
> Do you have any recommendation on how to deal with this?
>
> Thank you,
> Sophie
>
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