Hi all,
Is using forced permutation for non-orthogonal design matrices wrong or is it allowed to do this instead of using tools like palm (what happens eg with the covariates when using forced permutation)? I used forced permutation and it seemed to work, results were (partly) comparable to what I found with monte carlo simulations. Thanks, Maaike ________________________________ Van: freesurfer-boun...@nmr.mgh.harvard.edu <freesurfer-boun...@nmr.mgh.harvard.edu> namens Harms, Michael <mha...@wustl.edu> Verzonden: vrijdag 26 augustus 2016 01:00:13 Aan: Freesurfer support list Onderwerp: Re: [Freesurfer] mri_glmfit-sim permutation testing running after 3 days! Hi, You might want to check out FSL’s PALM tool, which has a bit more sophisticated permutation framework, and allows for permutation in the context of non-orthogonal covariates. cheers, -MH -- Michael Harms, Ph.D. ----------------------------------------------------------- Conte Center for the Neuroscience of Mental Disorders Washington University School of Medicine Department of Psychiatry, Box 8134 660 South Euclid Ave. Tel: 314-747-6173 St. Louis, MO 63110 Email: mha...@wustl.edu From: <freesurfer-boun...@nmr.mgh.harvard.edu<mailto:freesurfer-boun...@nmr.mgh.harvard.edu>> on behalf of Ajay Kurani <dr.ajay.kur...@gmail.com<mailto:dr.ajay.kur...@gmail.com>> Reply-To: Freesurfer support list <freesurfer@nmr.mgh.harvard.edu<mailto:freesurfer@nmr.mgh.harvard.edu>> Date: Thursday, August 25, 2016 at 4:13 PM To: Freesurfer support list <freesurfer@nmr.mgh.harvard.edu<mailto:freesurfer@nmr.mgh.harvard.edu>> Subject: Re: [Freesurfer] mri_glmfit-sim permutation testing running after 3 days! Hi Doug, Thanks for the help! I think I figured out the issue based on your response. 1) I created a template to use for this group and named it fsaverage (including creating monte carlo simulations) for simplicity of integrating with freesurfer as I am newer to it. This is why the sizes didn't match up as you expected but the mri_glmfit still ran. 2) I deleted the folder and restarted without background processes. The error became apparent. Of my covariates (2 fix factors and 3 quantitative), not all were orthogonal. In looking at the error more, it seems that i need to add the --perm-force if I wanted the simulation to run, however the background processes were not aware of this error and kept polling as you mentioned. This brings me to a new but related issue. From what I have read in other freesurfer posts, it is statistically incorrect to use --perm-force for non-orthogonal covariates (or continuous covariates). I am unsure how to proceed. a) If I ran permutation testing (to overcome the issue of incorrect smoothness estimations from the gaussian distribution assumption), then I run into the issue of non-orthogonal covariates. Is there a way to orthogonalize the data in freesurfer, or a solution to this issue? b) If orthogonalizing is difficult to implement, another option is running Qdec with the montecarlo simulation at a more conservative p value (p< 0.001). From your previous posts, the testing at this p value for 10mm seems to meet the 5% FPR. One question is if the non-orthogonal data affects this analysis as well for this model? Thanks, Ajay On Thu, Aug 25, 2016 at 12:18 PM, Ajay Kurani <dr.ajay.kur...@gmail.com<mailto:dr.ajay.kur...@gmail.com>> wrote: Hi Freesurfer Experts, I am trying to use freesurfer's mri_glmfit-sim tool to run permutation testing on cortical thickness data (as recommended by Doug in my previous post: http://www.mail-archive.com/freesurfer%40nmr.mgh.harvard.edu/msg48653.html ) Most of the tutorials I found were not related to permutation testing so the subsequent steps may be incorrect. Please let me know where I go wrong... 1) I first ran QDec to generate a folder for the analysis which would create the subsequent fsgd and y files needed my mri_glmfit-sim. I am running both left and right hemisphere cortical thickness analysis with 10mm smoothing. The following is for just the left hemisphere. Note I am doing a 3 group comparison, but for this 2 group ttest I manually centered the data based on the 3 group mean for age and education. 2) I ran the following command: /mri_glmfit-sim --glmdir ./HCvsPAT_lh_thickness_10mm/ --sim perm 10000 2 perm.abs.2 --sim-sign abs --bg 16 Prior to running the command above, from the y.fsdg file I deleted the fwhm estimate of 13mm since this was not correctly estimated (ACF with long tails). I assumed that by removing this estimate, it would force the permutation test to calculate based on the data but when looking at the log output I see the following which says fwhm 0: cmdline mri_glmfit.bin --C ./HCvsPAT_lh_thickness_10mm//tmp.mri_glmfit-sim-19468/lh-Avg-Intercept-thickness.mtx --C ./HCvsPAT_lh_thickness_10mm//tmp.mri_glmfit-sim-19468/lh-Diff-Male-Female-Intercept-thickness.mtx --C ./HCvsPAT_lh_thickness_10mm//tmp.mri_glmfit-sim-19468/lh-Diff-PD-MCI-Intercept-thickness.mtx --C ./HCvsPAT_lh_thickness_10mm//tmp.mri_glmfit-sim-19468/lh-X-Gender-Group-Intercept-thickness.mtx --sim perm 625 2 ./HCvsPAT_lh_thickness_10mm//csd/perm.abs.2.j013 --y /home/akurani/Documents/PPMI/FS_Final/qdec/HCvsPAT_lh_thickness_10mm/y.mgh --mask ./HCvsPAT_lh_thickness_10mm//mask.mgh --sim-sign abs --fwhm 0 --fsgd ./HCvsPAT_lh_thickness_10mm//y.fsgd dods --surf fsaverage lh white --sim-done ./HCvsPAT_lh_thickness_10mm//csd/poll/done.perm.abs.2.j013 3)I started this a few days ago on a 16 core machine and it is still running in the terminal. I have 150 subjects in the analysis and specified 10000 iterations. In the terminal I assumed when I reach Poll 10000 it would be complete but currently I am at : Poll 13341 job 1 Thu Aug 25 12:03:51 CDT 2016 Questions: a) I am curious, is this going to run 10,000 simulations X 150 patients or does the Poll number not have anything to do with the number of iterations it is on? b) Did I run this procedure correctly? Was I incorrect in deleting the fwhm estimate from y.fsgd file generated by Qdec even though we know the estimate is incorrect since smoothness assumed a gaussian distribution as opposed to gaussian with heavy tails c) I noticed in the logfile the following warning: INFO: gd2mtx_method is dods Computing normalized matrix Normalized matrix condition is 5.65727 Matrix condition is 935.597 Found 136777 voxels in mask Reshaping mriglm->mask... search space = 89675.729228 ERROR: design matrix is not orthogonal, cannot be used with permutation. If this something you really want to do, run with --perm-force Poll 2 job 1 Tue Aug 23 22:58:18 CDT 2016 I am not sure if this means my simulation is incorrect? Thanks, Ajay ________________________________ The materials in this message are private and may contain Protected Healthcare Information or other information of a sensitive nature. If you are not the intended recipient, be advised that any unauthorized use, disclosure, copying or the taking of any action in reliance on the contents of this information is strictly prohibited. If you have received this email in error, please immediately notify the sender via telephone or return mail.
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