Do you suggest using random-effect model? Is there any problem with using a fix-effect model (other than the fact that by using this model we can not predict response of subjects outside our population)?
On Wed, Oct 19, 2011 at 3:07 PM, Douglas N Greve <gr...@nmr.mgh.harvard.edu>wrote: > > It should be roughly the sum of the dofs of the individual subjects. Why > are you using a fixed-effects model? > doug > > SHAHIN NASR wrote: > >> Thanks Doug. Just one related question. Should I also generate a new >> ffxdof.dat file for this map? I assumed that ffxdof depends on the number of >> subjects (session) and since number of subjects (sessions) is the same >> between the two groups then I can use those values, generated by >> isxconcat-sess for either map1 or map2. Right? >> >> >> >> On Wed, Oct 19, 2011 at 1:33 PM, Douglas N Greve < >> gr...@nmr.mgh.harvard.edu >> <mailto:gr...@nmr.mgh.harvard.**edu<gr...@nmr.mgh.harvard.edu>>> >> wrote: >> >> Hi Shahin, it is not as simple as doing a subtraction of the >> cesvar files. What you are trying to get is the expected variance >> of your difference between the ces files (as a variance, it must >> be positive). To get this you need >> >> cesvardiff = (cesvar1+cesvar2)/(2^2) >> >> The 2^2 is the number of inputs (2) squared. >> >> doug >> >> >> SHAHIN NASR wrote: >> >> Hi, >> >> I have generated two different functional connectivity maps >> for two different ROI-based seeds. These maps are based on >> group-average of the same subjects (generated by using >> separate isxconcat-sess commands ), and now I want to see the >> difference map. To do so, I used mris_calc as below. >> > mris_calc -o diff_map/rh.ces.nii map1/rh.ces.nii sub >> map2/rh.ces.nii >> >> Also, to generate the rh.cesvar.nii file I used this command: >> > mris_calc -o diff_map1/rh.cesvar.nii map1/rh.cesvar.nii >> sub map2/rh.cesvar.nii >> >> But then when I used the glmfit with WLS option as below: >> >> > mri_glmfit --y rh.ces.nii --osgm --glmdir rh.ffx.osgm.wls >> --nii --mask ../rh.mask.nii --yffxvar rh.cesvar.nii >> --ffxdofdat ../ffxdof.dat --surf fsaverage rh --wls rh.cesvar.nii >> >> I faced an error saying: "Error: MRInormWeights: values less >> than or eq to 0" which I assumed is related to an error in >> rh.cesvar.nii file (am I right?). Would you tell me how can I >> fix this problem? >> >> P.S.: please note that sequence of subjects and all MRI >> parameters are exactly the same between the two maps. >> >> -- Shahin Nasr >> >> PhD in Cognitive Neuroscience >> Martinos Imaging Center, MGH >> Harvard Medical School >> >> >> -- Douglas N. Greve, Ph.D. >> MGH-NMR Center >> gr...@nmr.mgh.harvard.edu >> <mailto:gr...@nmr.mgh.harvard.**edu<gr...@nmr.mgh.harvard.edu> >> > >> Phone Number: 617-724-2358 <tel:617-724-2358> Fax: 617-726-7422 >> <tel:617-726-7422> >> >> Bugs: >> surfer.nmr.mgh.harvard.edu/**fswiki/BugReporting<http://surfer.nmr.mgh.harvard.edu/fswiki/BugReporting> >> >> <http://surfer.nmr.mgh.**harvard.edu/fswiki/**BugReporting<http://surfer.nmr.mgh.harvard.edu/fswiki/BugReporting> >> > >> FileDrop: >> www.nmr.mgh.harvard.edu/**facility/filedrop/index.html<http://www.nmr.mgh.harvard.edu/facility/filedrop/index.html> >> >> <http://www.nmr.mgh.harvard.**edu/facility/filedrop/index.**html<http://www.nmr.mgh.harvard.edu/facility/filedrop/index.html> >> > >> >> >> >> >> The information in this e-mail is intended only for the person to >> whom it is >> addressed. If you believe this e-mail was sent to you in error and >> the e-mail >> contains patient information, please contact the Partners >> Compliance HelpLine at >> >> http://www.partners.org/**complianceline<http://www.partners.org/complianceline>. >> If the e-mail was sent to >> you in error >> but does not contain patient information, please contact the >> sender and properly >> dispose of the e-mail. >> >> >> >> >> -- >> Shahin Nasr >> >> PhD in Cognitive Neuroscience >> Martinos Imaging Center, MGH >> Harvard Medical School >> >> > -- > Douglas N. Greve, Ph.D. > MGH-NMR Center > gr...@nmr.mgh.harvard.edu > Phone Number: 617-724-2358 Fax: 617-726-7422 > > Bugs: > surfer.nmr.mgh.harvard.edu/**fswiki/BugReporting<http://surfer.nmr.mgh.harvard.edu/fswiki/BugReporting> > FileDrop: > www.nmr.mgh.harvard.edu/**facility/filedrop/index.html<http://www.nmr.mgh.harvard.edu/facility/filedrop/index.html> > > -- Shahin Nasr PhD in Cognitive Neuroscience Martinos Imaging Center, MGH Harvard Medical School
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