On Fri, 25 Jan 2019, Ben Smith wrote: > Hi all,
> I have a dataset with TR=2 where I want to delete the first 10 TRs (first > 20 seconds) before running fit_event_hrf_model. > Deleting the first TRs is easy: > ds = ds[10:] > However I am unsure what to do with time coordinates. I understand that if > I adjust the onsets in the event list then I will also need to adjust the > time_attr in the dataset, like: > TR=2 > for e in event_list: > e['onset'] = e['onset']-10*TR > ds = ds.sa.time_coords - 10 * TR > result= fit_event_hrf_model(ds, event_list, time_attr='time_coords', > > condition_attr=('targets', 'chunks')) > My intuition is that it shouldn't matter whether you adjust event onset > and ds time coordinates as long as you adjust both or neither - so that > they stay correctly aligned. sounds true to my understanding too > But when I run this and test, then I do get slightly different estimates > depending solely on whether I adjust the both time coordinates and event > onsets, or neither (keeping constant the removal of 10 trs). hm, if anything, I would trust the one where you do remove since may be there is some hardcoded assumption of time to start from 0? anyways -- first step might be to check your .sa.regressors you get from both solutions -- do they look as expected or which one is screwed up? -- Yaroslav O. Halchenko Center for Open Neuroscience http://centerforopenneuroscience.org Dartmouth College, 419 Moore Hall, Hinman Box 6207, Hanover, NH 03755 Phone: +1 (603) 646-9834 Fax: +1 (603) 646-1419 WWW: http://www.linkedin.com/in/yarik _______________________________________________ Pkg-ExpPsy-PyMVPA mailing list Pkg-ExpPsy-PyMVPA@alioth-lists.debian.net https://alioth-lists.debian.net/cgi-bin/mailman/listinfo/pkg-exppsy-pymvpa