Dear members,
When i do a PCA in melodic, i get the following message:
> Excluding voxels with constant value
> Data size : 120 x 158227
> Removing mean image ... done
> Estimating data covariance ... done
> Removing mean time course ... done
> Starting PCA ... done
So, it seems that you center the data BOTH for the lines and the columns.
I thought that if you make a spatial PCA, you should center the data
only for the variables (time) and not for the statistical units (space):
removing mean tim course only.
In a temporal PCA i thought you should also center only for the
variables (space in this case): removing mean image only.
Am i right? Do you have a theoretical justification for the procedure
used in Melodic?
Best regards,
Pierre Lafaye de Micheaux, Ph.D.
--
Pierre Lafaye de Micheaux
Bureau 210, bâtiment BSHM
1251 avenue centrale BP 47
38040 GRENOBLE Cedex 09
FRANCE
Tél.: 04.76.82.58.73 / Fax: 04.76.82.56.65
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