[Mne_analysis] Calculate the planar gradient

Alexandre Gramfort alexandre.gramfort at inria.fr
Fri Jan 25 05:16:02 EST 2019
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hi,

have a look at :
https://martinos.org/mne/dev/auto_examples/preprocessing/plot_virtual_evoked.html

Alex

On Wed, Jan 23, 2019 at 12:12 AM Narun Pornpattananangkul
<narunzhang at gmail.com> wrote:
>
>         External Email - Use Caution
>
>
> Hi MNE users/developers,
>
> I am trying to move away from Matlab, and I was wondering if MNE python has a function to compute the planar gradient from the axial gradiometers. I was told that it is more appropriate to use planar gradient for the sensor-level type of analysis.
>
> Fieldtrip has ft_megplanar and ft_combineplanar functions for this.
> http://www.fieldtriptoolbox.org/reference/ft_megplanar/
> http://www.fieldtriptoolbox.org/reference/ft_combineplanar/
>
> From their tutorial http://www.fieldtriptoolbox.org/tutorial/eventrelatedaveraging/:
> "The planar gradient at a given sensor location can be approximated by comparing the field at that sensor with its neighbors (i.e. finite difference estimate of the derivative). The planar gradient at one location is computed in both the horizontal and the vertical direction with the FieldTrip function ft_megplanar. These two orthogonal gradients on a single sensor location can be combined using Pythagoras rule with the FieldTrip function ft_combineplanar."
>
> If you do not have such functions, what might be workaround?
>
> Thank you so much,
>
> Narun
>
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