[R] mgcv: Extract random effects from gam model

[Simon Wood]

Hi Jan ,

coef(mod) will extract the coefficients, including for a. They are 
labelled and for 'a' are in the same order as levels(a).

best,
Simon



On 23/07/12 10:08, janvanhove wrote:
> Hi everyone,
>
> I can't figure out how to extract by-factor random effect adjustments from a
> gam model (mgcv package).
>
> Example (from ?gam.vcomp):
> library(mgcv)
> set.seed(3)
> dat <- gamSim(1,n=400,dist="normal",scale=2)
> a <- factor(sample(1:10,400,replace=TRUE))
> b <- factor(sample(1:7,400,replace=TRUE))
> Xa <- model.matrix(~a-1)    ## random main effects
> Xb <-  model.matrix(~b-1)
> Xab <- model.matrix(~a:b-1) ## random interaction
> dat$y <- dat$y + Xa%*%rnorm(10)*.5 +
>    Xb%*%rnorm(7)*.3 + Xab%*%rnorm(70)*.7
> dat$a <- a;dat$b <- b
>
> mod <- gam(y ~ s(a, bs="re") + s(x2, k = 15), data = dat)
>
> When I run plot(mod) I can see the adjustments for the "a" factor, but I
> don't know which adjustment is associated with which factor. Is it possible
> to extract the information underlying this plot numerically?
>
> Thanks!
> Jan
>
>
>
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-- 
Simon Wood, Mathematical Science, University of Bath BA2 7AY UK
+44 (0)1225 386603               http://people.bath.ac.uk/sw283