Interaction between category specific effects in brms

Please also provide the following information in addition to your question:

  • Operating System: Windows 10
  • brms Version: 2.11.1

Dear all,

I am trying to use category-specific effects in an adjacent category model. It looks really useful for the question that I have. I have two binary predictors, but ideally I also want to investigate the interaction of the two variables.

However, when trying to have an interaction between the two category-specific predictors, I get the error that the interaction between the two is “invalid syntax”. In addition, I can nowhere find information about interactions between category-specific predictors.

Is it indeed the case that category-specific predictors cannot be specified as an interaction (yet)? And if so, is there a possible workaround for this?

Thanks in advance!

Without seeing the code you used it is pretty much impossible to debug your problem. Can you post what you have tried?

OK, I just realized I overlooked one option, namely specifying the full interaction within the cs() command, instead of running cs()*cs() or cs():cs(). And that seems to work perfectly.

Sorry for wasting your time!