Thank you Douglas !
You need to weight by the number of vertices
n = [27805 2321 552];
m = [8.8194 10.3661 10.3365];
sum(n.*m)/sum(n)
ans =
8.9637
On 11/10/2016 06:44 AM, Matthieu Vanhoutte wrote:
> Dear Freesurfer's experts,
>
> Could anyone please explain me the difference I got with command line
> in below mail ?
>
> Best regards,
> Matthieu
>
> 2016-08-12 12:07 GMT+02:00 Matthieu Vanhoutte
> <matthieuvanhoutte@gmail.com <mailto:matthieuvanhoutte@gmail.com >>:
>
> Dear experts,
>
> I am in trouble with two ways of computing mean intensity with
> mri_segstats.
>
> First I have used on .annot files with three different labels
> inside (SegId 1 to 3) :
>
> /mri_segstats --annot fsaverage lh cache.th23.pos.sig.ocn.annot
> --i lh.PET.fsaverage.sm10.mgh --sum lh.pet.sum/
> /
> /
> which give me those results:
> # ColHeaders Index SegId NVertices Area_mm2 StructName Mean
> StdDev Min Max Range
> 1 1 27805 14182.6 cluster-001 8.8194 1.4351
> 6.2105 14.2947 8.0842
> 2 2 2321 1047.3 cluster-002 10.3661 1.0848
> 8.8375 12.9317 4.0942
> 3 3 552 313.1 cluster3 10.3365 0.4711
> 9.3719 11.8694 2.4975
>
> Second I have created on .label files containing the three
> segmented labels (SegId 1 to 3) and used this label with mri_segstats:
>
> /mri_segstats --slabel fsaverage lh
> lh.th23.cluster.thresh1.3.label --i lh.PET.fsaverage.sm10.mgh
> --excludeid 0 --sum lh.pet.label.sum /
> /
> /
> which give me those results:/
> /
> /# ColHeaders Index SegId NVertices Area_mm2 StructName Mean
> StdDev Min Max Range /
> / 1 1 30678 15542.9 Seg0001 8.9637 1.4701 6.2105
> 14.2947 8.0842 /
> /
> /
> I verified if I obtained the same results with the two ways
> (.annot or .label) and everything is fine comparing NVertices,
> Area_mm2 but Mean in first way gives me (8.8194+10.3661+10.3365)/3
> = 9.84066 and with .label file Mean = 8.9637.
>
> Did I have miss anything and how is computed mean intensity ?
>
> Many thanks in advance.
>
> Best regards,
> Matthieu
>
>
>
>
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--
Douglas N. Greve, Ph.D.
MGH-NMR Center
greve@nmr.mgh.harvard.edu
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