nipype

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I'm using SPM functions for the 2nd level analysis and would like to use a covariate.

For example, OneSampleTTestDesign has an optional covariate argument:

covariates: (a list of items which are a dictionary with keys which
         are 'vector' or 'name' or 'interaction' or 'centering' and with
         values which are any value)
        covariate dictionary {vector, name, interaction, centering}

Description is fairly vague on how the values should look like. From the source code it is also not clear to me. I searched on various forums and Internet but couldn't find any example. Can anyone provide more detailed explanation and share some example code?

UPDATE: class MultipleRegressionDesign(FactorialDesign): part of the code is a bit more informative, gives mapping to the SPM object. Digging a bit into the SPM, this suggests the following format:

[{'centering': 1,
  'name': 'performance_mean',
  'vector': [1,2,3,...nsubjects]}]

where 1 in the centering variable should map to "Overall mean" in the SPM. Strangely, this part of the code does not exist in OneSampleTTestDesign, so I'm wondering whether covariates are taken into account there? Also, how to make sure these variables are associated to a correct subject/session?

@hstojic - this is quite old at this point and for a two sample t-test, but may help:

https://github.com/satra/sad/blob/master/spm_2lvl.py#L13

Thanks for the update @hstojic. It helped a lot in getting my multiple regression model working!

Thanks for the update @hstojic.