[R] Using random effects on gamm4

[Ramiro Barrantes]

My basic question is, how do I specify random effects in gamm4 properly?

Reproducible example:

library(gamm4)
library(ggplot2)

residualNoise <- 20
blockNoise<- 10
nBlocks <- 3
n<-100
df <- data.frame(x=rep(1:n,nBlocks),y=rep(0.01*(1:n)^2,nBlocks))
df$block <- rep(1:nBlocks,each=n)
blockNoise <- rnorm(nBlocks,mean=0,sd=blockNoise)
df$y <- df$y+blockNoise[df$block]
df$y <- df$y+rnorm(1:nrow(df),mean=0,sd=residualNoise)
df$block <- factor(df$block)

fit1<-gamm4(y~s(x),random=~(1|block),data=df)
df$predicted1 <- predict(fit1$gam)

ggplot(df,aes(x,y))+
  geom_point()+
  facet_wrap(~block)+
  geom_line(aes(x=x,y=predicted1),colour="red")

fit2<-gamm4(y~s(x)+s(block,bs="re"),data=df)
df$predicted2 <- predict(fit2$gam)

ggplot(df,aes(x,y))+
  geom_point()+
  facet_wrap(~block)+
  geom_line(aes(x=x,y=predicted2),colour="red")

With fit1 I am getting the same fit on every block, whereas on fit2 I am getting a different fit on every block, although in both I am specifying random effects on block.  I would expect different fits per block when specifying random effects on them.  Why doesn't it happen on fit1?

Thank you very much in advance for any insight.

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