Nipipe: concatenate analysis steps within and across sessions

[yuki1209]

Hello everyone,

I'm currently setting up my first nipype script and would like to ask a question.
I think sometimes we have to conduct analysis steps within or across sessions in each subject. I wonder how can we concatenate those steps?
For example (http://nbviewer.jupyter.org/urls/dl.dropbox.com/s/zjojdekdhjegr6j/pymvpa_preprocessing_haxby.ipynb), I want to change only realign step as conducted across sessions, keeping subsequent steps as conducted within sessions.
I would appreciate any suggestions or information.

Sincerely,
Yuki

[ashgillman]

Hi Yuki,
I'm not 100% sure what you are trying to do sorry. Are you trying to ensure that processing steps that are common across sessions are only conducted once? If so, Nipype will do this automatically. After you set an iterable, only nodes that depend on that iterable are actually run multiple times.

Or are you trying to combine the processed data from all sessions for each subject and perform some analysis on what is changing across sessions? Check out the JoinNode http://nipype.readthedocs.io/en/latest/users/joinnode_and_itersource.html

Ash