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Hi everyone,

I'm trying to run gPPI analysis on first levels done in FSFAST using the PPPI_FSFAST_WRAPPER and the  FSFAST2SPM script. I'm running into the following error in Matlab:

Reference to non-existent field 'W'.

Error in PPPI (line 668)
        W      = SPM.xX.W(Sess.row,Sess.row);

Error in PPPI_FSFAST_WRAPPER (line 101)
            PPPI([Directory filesep Subjects{ii} '_PPI_config.mat'])

Looks like the SPM.xX.W field is never declared, hence the error. According to the comments in PPPI, the 'W' field specifies the  "whitening matrix (NB: confounds have already been whitened)".

I've tried initializing the SPM.xX.W field in the FSFAST2SPM wrapper, in the "Fill in SPM Structure" section, but still end up with the same error. Where should this field be initialized?

Thanks for your help,

Afsana