[R-sig-ME] MCMCglmm: ixn between binary family-level factor and us() random effect
Paul.Johnson at glasgow.ac.uk
Sat Feb 5 04:37:46 CET 2011
I'm fitting models to estimate mother-father and parent-offspring covariances, using
random = ~us(offpar.f):famid
where offpar.f is a factor with 3 levels: offspring, mother, father and "famid" is the family ID. This allows me to compare the strengths of mother-offspring and father-offspring correlations within familes. The next step is to compare these covariances between asthma families (AF) and non-asthma families (NAF). I.e. I want to estimate three covariances within each level of the NAF/AF factor while setting the covariances between NAF and AF families to zero. The structure of the 6x6 covariance matrix should be
where VAF and VNAF are 3x3 US covariance matrices and the 0s are 3x3 blocks of zeros.
How can I specify this in a formula? I've tried various random formulae based on what I found in the MCMCglmm course notes and this list but with no success.
Thanks for any help,
The University of Glasgow, charity number SC004401
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