Reply-To: | | [log in to unmask][log in to unmask]> 8/7/2007 6:05 AM >>> > > Hi Darren and Shelly > > I had this problem previously, it's not serious (thanks to > Karl for an off-list answer). > > I found an apparently singular covariance matrix C at the > deconvolution step which causes an error in spm_PEB from line > 351 in spm_peb_ppi, i.e. > C=spm_PEB(Y,P). > > This turned out to be due to a sparse matrix inversion > setting in spm_PEB and is not a serious problem but can be > resolved by setting exp(-32) to > exp(-16) in > > line 371 (of spm_PEB) ==> C = inv(C + speye(length(C))*exp(-32)); > > This makes sure that C is not too close to singular and > inversion proceeds without warnings. > > Hope this helps > > Alexa > > > > -----Original Message----- > From: SPM (Statistical Parametric Mapping) > [mailto:[log in to unmask]] On Behalf Of d gitelman > Sent: 07 August 2007 00:47 > To: [log in to unmask] > Subject: Re: [SPM] PPI Analysis: SPM5 Produces Matlab Warning > > Hi Shelly: > > Could you please provide a bit more information > > 1) How many conditions for each session and which ones are > you modeling. > Also how many trials per condition per session? > > 2) Does the warning occur for every PPI calculation. If you > use a multisession spm i assume you are calculating 2 PPI's > per subject. > > 3) what is the version of spm.m, of spm_peb_ppi.m and of > spm_regions.m. You can used the attached script to return the > version strings. Put the script somewhere in your matlab > path. Start matlab. cd to the spm5 directory and type > retVer('spm.m'), etc. > > darren > > > -----Original Message----- > > From: SPM (Statistical Parametric Mapping) > [mailto:[log in to unmask]] > > On Behalf Of Shelly Fitzgerald > > Sent: Friday, August 03, 2007 6:03 PM > > To: [log in to unmask] > > Subject: [SPM] PPI Analysis: SPM5 Produces Matlab Warning > > > > Dear SPM'ers, > > > > I have a question regarding PPI using SPM5. Thus far I've > conducted > > the following steps: > > > > 1. run 1st level stats (2 sessions per subject; each > session modeled > > separately in the same design) 2. extract VOIs for each session 3. > > calculate PPI regressors for each VOI > > > > While calculating the PPI regressors, however, I receive > the following > > matlab warning: > &•|ü"b |