# [Simnibs-discuss] Focality with a specific threshold

Oula Puonti oulap at drcmr.dk
Wed Nov 16 11:49:40 CET 2022

```Hi Laurent,

Please see here for the function that calculates the field_summary:

https://github.com/simnibs/simnibs/blob/master/simnibs/msh/mesh_io.py#L2231

If you want to calculate a different percentile you can do this (in python):

from simnibs.msh import mesh_io

#This produces volumes with 50%tile

m.fields_summary(roi=2, percentiles=)

#This produces areas

m.fields_summary(roi=1002, percentiles=)

Note that the output units differ between the two calls, for volumes it
will be mm^3 and for areas it will be mm^2. This will depend on the roi
you pass. roi=2 means that you calculate the volume of the tetrahedra
where the field is higher than the %tile you define, whereas for
roi=1002 calculates the area of the triangles the same way.

Best,

Oula

On 11/15/22 10:49, LAURENT TORLAY wrote:
>
> Hello,
>
> First, I use Simnibs for several years and thank you for developping
> such a software !
> My question : in the file fields_summary.txt, focality is measured by
> 'area with a field >= X% of the 99.9th percentile', how can we get a
> similar measurement with a specific threshold in V/m ? (moreover, why
> the result is a volume ? The area is multiplied by a mean cortical
> thickness (of the area, the whole brain ?) )
> Best,
>
> L. Torlay
>
>
> _______________________________________________
> Simnibs-discuss mailing list
> Simnibs-discuss at drcmr.dk
> https://mailman.drcmr.dk/mailman/listinfo/simnibs-discuss
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