[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.
Cheers,
Jarrod
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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