Variance structures for residuals - brms

Interfaces brms
1

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

  • Operating System: debian 9
  • brms Version: brms_2.8.0

Hi all,

Just trying brms for the first time so sorry if I’m asking something ignorant.

I wanted to know if there was a way to specify the variance structure of the residuals. I work on clonal organisms that I measure in different environments and treat the response variable as two separate responses (one for each environment in a 2 environment case).

At the group level I’m able to estimate the covariance between responses but as no individual organism is measured in both environments I can’t estimate the residual covariance.

When using programs such as asreml-R or MCMCglmm, I can use the idh() variance structure that estimates seperate residual variances for each response but not the covariance.

Is there an equivalent in brms?

thanks,
Adam

2

In brms, you can either fit the full residual correlation matrix (available for a few families only currently) or assume residual correlations to be zero. You can control this by using the set_rescor function.

3

Thanks for the tip Paul.