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Mark, isn't this what the stats/sigmasquareds volume is? btw, the avwmaths cmd below will under estimate the variance slightly as it will take into accnt the proper DOF. doug Mark Jenkinson wrote: > Hi, > > You can calculate the voxel-wise variance from the 4D residuals > by using > avwmaths++ res4d -Tstd -sqr variance_map > > That should be what you want. > > All the best, > Mark > > > > On 5 Jan 2007, at 19:55, Clare Kelly wrote: > >> Thanks Michael, I had seen that but what I was thinking of was a 2D >> file that gives one value for the error variance for each voxel - in >> the same way that the varcope images provide a measure of how much >> signal is not accounted for by one particular EV - how do I calculate >> this for the whole model... or does that not make sense?!? >> >> Thanks! >> Clare >> >> On 1/5/07, Michael Hanke <[log in to unmask]> wrote: >> >>> Hi, >>> >>> On Fri, Jan 05, 2007 at 06:30:44PM +0000, Clare Kelly wrote: >>> > Hi all, >>> > >>> > I apologise if this is a really basic question but I can't seem >>> to find the answer I'm looking for in the >>> > archive. >>> > >>> > I want to calculate the residuals for a particular model that >>> included 4 task regressors plus their >>> > temporal derivatives, 8 nuisance regressors, and 6 motion >>> parameters, as I want to compare the >>> > residuals between different models with different numbers of >>> regressors. >>> > >>> > I understand that each varcope gives me the error related to that >>> particular EV, but I'm not clear on >>> > how I combine them - I have looked at section 14.5 of the Jezzard >>> et al. book but I still don't know >>> > what to do. >>> FEAT can output the residuals for you (no need to calculate anything). >>> In fact it always stores them to disk, but deletes them at the end of >>> the analysis. Just look at the end of you design.fsf file and you'll >>> see: >>> >>> # Delete GLM residuals? >>> set fmri(cleanup_residuals_yn) 1 >>> >>> Change this default into: >>> >>> # Delete GLM residuals? >>> set fmri(cleanup_residuals_yn) 0 >>> >>> and you'll find a res4d.nii.gz (or whatever suffix) in the stats >>> directory when Feat is finished. >>> >>> HTH. >>> >>> >>> Cheers, >>> >>> Michael >>> >>> >>> >>> -- >>> GPG key: 1024D/3144BE0F Michael Hanke >>> http://apsy.gse.uni-magdeburg.de/hanke >>> ICQ: 48230050 >>> > > -- Douglas N. Greve, Ph.D. MGH-NMR Center [log in to unmask] Phone Number: 617-724-2358 Fax: 617-726-7422 In order to help us help you, please follow the steps in: surfer.nmr.mgh.harvard.edu/fswiki/BugReporting