[R-sig-ME] informative priors in MCMCglmm

Jarrod Hadfield j.hadfield at ed.ac.uk
Sat Feb 14 09:03:58 CET 2015

HI Diane,

Sorry for the delay. You can't place a prior directly on the  
heritability in MCMCglmm (you would have to use JAGS/WinBUGS to do  
that). You can place priors on the variance components though. You  
have the choice of inverse Wishart priors (aka inverse gamma or  
inverse scaled chi-square in the univariate case) or parameter  
expanded priors (setting nu=1 and alpha.mu=0 you have a scaled F(1,1)  
prior). The inverse Wishart prior is the easiest to understand:  
placing a prior of V=2, nu=1 on the additive genetic variance is  
equivalent to having a prior observation of a single breeding value of  
value sqrt(V). A prior of this strength sounds innocuous but it can  
have a surprisingly strong effect.



Quoting Diana Caro <dianacaro0918 at hotmail.com> on Mon, 26 Jan 2015  
09:58:46 -0500:

> Hi!
> I want to estimate variance components for four weight traits in a  
> multivariate model.If I have prior information of variances or  
> heritabilities (from literature), how can I incorporate this  
> information in a prior?
> Thanks
> Diana
> 	[[alternative HTML version deleted]]
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