Dear Tim,
Tim Hahn wrote:
> Dear SPMers,
> I would like to retrieve the betas for an area of which a have a mask. How
> could I get these betas?
> Additionally: is there a list of which data is stored in which workspace
> variable in SPM5?
The betas are stored in images in the directory in which you did the
analysis eg. beta_0001.img is an image of the first regression
coefficient.
You can use the display button in SPM, load these images, type in the
relevant co-ordinates and see the beta value ('intensity:').
For lots of voxels you could link to the file from the matlab workspace eg.
>V=spm_vol('DIRECTORY-PATH\beta_0001');
then create a list of N voxels you want to look at
by specifying their locations in a 3 x N XYZ matrix
eg. XYZ(:,1)=[-20,-20,5) % first voxel location
XYZ(:,2)=[-20,20,5) % second voxel location
then get the beta values
> beta=spm_get_data(V,XYZ)
Using similar principles you could create the XYZ list automatically
by loading in a mask image. Getting all the data from a large range of
voxels, then eliminating those voxels not in the mask. Or perhaps
someone else has already written this piece of code !
Best,
Will.
> Thanks in advance!
> Kind regards,
> Tim
>
>
--
William D. Penny
Wellcome Trust Centre for Neuroimaging
University College London
12 Queen Square
London WC1N 3BG
Tel: 020 7833 7475
FAX: 020 7813 1420
Email: [log in to unmask]
URL: http://www.fil.ion.ucl.ac.uk/~wpenny/
