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Dear SPM, w/r to the below mentioned email, I have a further question: I have a data set for which I want to discard the final scan belonging to the last active epoch. That makes my final epoch 1 scan shorter (n-1) than the other epochs of n scans. Calling fixed durations & entering "n" for duration of epochs returns no error message, but obviously due to the onset specification, the final epoch will be just n-1 long. Does that mean, SPM does not mind "to be cut off " in specifying the design matrix for a final but shorter epoch? TIA- Andreas **************************************************************************** ******* Dr. Andreas J. Bartsch phone: +49 (0)931-201-0 Division of Neuroradiology, ecr.: -5791 BJMU Wuerzburg pager: #5325 Josef-Schneider-Str. 11 fax: +49 (0)931-201-2685 97080 Wuerzburg email: [log in to unmask] Germany [log in to unmask] **************************************************************************** ******* Date: Fri, 28 Apr 2000 17:13:48 +0100 (BST) Reply-To: Karl Friston <[log in to unmask]> Sender: spm From: Karl Friston <[log in to unmask]> Subject: Re: fMRI analysis bug? Dear Eric, > I have encountered what appears to be a bug in the "specify design" > component of the fMRI module. After determining the onsets of a given > condition (in the "variable SOAs" path) one is then asked to specify > the durations of each occurrence of that condition (in the "variable > durations" path). But, several steps later one is asked to specify a > (single) duration for each condition, apparently in ignorance of the > fact that one has specified a vector of such durations for each > condition previously. Moreover, what one enters at this point seems to > override the vector of durations entered first. So, it seems that one > cannot incorporate variable epoch durations into the design matrix. Am > I missing something or is this a bug? There have been a few emails about this. The critical thing to remember is that variable duration epochs are modeled as trains of events. You should therefore specify events (not epcochs) at the later stage. All the very best - Karl %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%