yep, those are typos. I just fixed them. thanks doug Jose Luis Cantero Lorente wrote: > Thanks Doug for your reply. I forgot that the number of columns is > number of classes by number of covariates +1. > > So, I only want you to confirm me that the extra zero that I've seen > in the FSwiki example is an erratum (see contrasts 7 and 8 in Four > Groups (2 Factors, Two Levels), One Covariate. DODS only. QDEC-able > <http://surfer.nmr.mgh.harvard.edu/fswiki/Fsgdf4G1V>) and that I don't > have to add any extra zero per covariate when testing the interaction > effect. > > Many thanks again. > Jose > > ----- Mensaje original ----- > De: Douglas N Greve <gr...@nmr.mgh.harvard.edu> > Fecha: Martes, 18 de Enero de 2011, 16:53 > Asunto: Re: [Freesurfer] contrast matrix for 2 discrete factors and 3 > continuous variables > A: Jose Luis Cantero Lorente <jlcan...@upo.es> > CC: freesurfer@nmr.mgh.harvard.edu > > > Hi Jose, with 6 classes and 3 continuous variables, I think you > > should have 24 regressors, which means 24 columns in the > > contrast matrix. Yours only has 18. Otherwise the contrast to > > test between B and C is correct (just need to add 6 zeros). For > > the interaction, you would need > > > > 0 0 0.5 -0.5 -0.5 0.5 0 0 .... > > > > doug > > > > Jose Luis Cantero Lorente wrote: > > > > > >Dear Freesurfers, > > > > > > > > >My experimental design includes 2 discrete factors and 3 > > continuous variables: > > > > > > > > >Discrete factors: > > > > > >- Diagnosis with three > > levels (A, B, C) > > > > > >- Gender with two levels > > (Males, Females) > > > > > > > > >Continuous variables: > > > > > >- Mean cortical thickness > > in the left hemisphere (CTLH) > > > > > >- Age > > > > > >- Performance in a memory > > test (TASK) > > > > > > > > >The FSGD file would be as follows: > > > > > > > > >GroupDescriptorFile 1 > > > > > >Title Thickness-subj > > > > > >Class AMale > > > > > >Class AFemale > > > > > >Class BMale > > > > > >Class BFemale > > > > > >Class CMale > > > > > >Class CFemale > > > > > >variables ZCTLH ZAGE > > > > > >Input control_01 AMale -1.04398 0.24789 > > > > > >Input control_02 AMale 1.22853 -0.72343 > > > > > >Input control_03 AFemale .13773 -1.37097 > > > > > >Input control_04 AFemale .41043 0.24789 > > > > > >Input mci_01 BMale -.77128 0.24789 > > > > > >Input mci_02 BMale -2.40749 0.73354 > > > > > >Input mci_03 BFemale -.86218 -1.0472 > > > > > >Input mci_04 BFemale .50133 0.23777 > > > > > >Input ad_01 CMale -.75678 0.22789 > > > > > >Input ad_02 CMale -2.88749 0.63047 > > > > > >Input ad_03 CFemale -.96015 -1.4452 > > > > > >Input ad_04 CFemale .80712 -0.37567 … > > > > > > > > >We are assuming different offsets and different slopes (DDOS). > > > > > > > > >The following contrast would test the null hypothesis whether > > there is a difference between B and C (T-test) regressing out > > the effect of the remaining variables. > > > > > > > > >0 0 0.5 0.5 -0.5 -0.5 0 0 0 0 0 0 0 0 0 0 0 0 > > > > > > > > >Could you help me to build the contrast for testing > > interactions in the above experimental design? In the FSwiki > > examples, you add one column when you have two factors with two > > levels each, and one continuous variable. I am not sure how many > > columns should I add in our particular case and why. > > > > > > > > >Null hypothesis: is there an interaction between diagnosis (B > > > C) and gender regressing out the two remaining variables? > > Assuming that you add one column per variable that is regressed > > out, the contrast would be as follows: > > > > > > > > >0 0 0.5 0.5 -0.5 -0.5 0 0 0 0 0 0 0 0 0 0 0 0 0 0 > > > > > > > > >Is this correct? Any help will be very appreciated. > > > > > > > > >Many thanks in advance. > > > > > > > > >Best regards, > > > > > >Jose > > > > > > > > >--- > > >Jose L. Cantero, Ph.D. > > >Laboratory of Functional Neuroscience > > >Department of Physiology, Anatomy and Cell Biology > > >University Pablo de Olavide > > >Ctra. de Utrera, Km.1 > > >41013 - Seville > > >- Spain - > > >Phone: +34 954 977433 > > >Fax: +34 954 349151 > > >Email: jlcan...@upo.es > > >http://www.upo.es/neuroaging/en/ > > >---------------------------------------------------------------- > > -------- > > > > > >_______________________________________________ > > >Freesurfer mailing list > > >Freesurfer@nmr.mgh.harvard.edu > > >https://mail.nmr.mgh.harvard.edu/mailman/listinfo/freesurfer > > > > -- > > 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 > > FileDrop: 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 . 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. > > > > --- > Jose L. Cantero, Ph.D. > Laboratory of Functional Neuroscience > Department of Physiology, Anatomy and Cell Biology > University Pablo de Olavide > Ctra. de Utrera, Km.1 > 41013 - Seville > - Spain - > Phone: +34 954 977433 > Fax: +34 954 349151 > Email: jlcan...@upo.es > http://www.upo.es/neuroaging/es/
-- 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 FileDrop: www.nmr.mgh.harvard.edu/facility/filedrop/index.html _______________________________________________ Freesurfer mailing list Freesurfer@nmr.mgh.harvard.edu https://mail.nmr.mgh.harvard.edu/mailman/listinfo/freesurfer
