[R-sig-ME] Can we do b-spline within lmer function?

[Ken Beath]

On 15/01/2008, at 9:42 AM, Zhong, Xiao wrote:

> Thanks, Ken.
>
> I tried your advice on my model:
>
> model2.growth.mcas5 <- lmer(response ~ bs(monthElapsed) + skills +  
> (1|studentID), data= mcas5, family=binomial(link="logit"), control =
> list(msVerbose = 1, usePQL = FALSE))
>
> It worked! What it gave me is:
>
>                      (Intercept)                   
> bs(monthElapsed)1                   
> bs(monthElapsed)2                  bs(monthElapsed)3
>                        -0.1509712                           
> 0.7019262                          
> -0.1934738                          0.6257330
>                  skillsG-Geometry                skillsM- 
> Measurement    skillsN-Number-Sense-Operations skillsP-Patterns- 
> Relations-Algebra
>                        -0.4333880                          
> -0.9468761                           
> 0.5263370                          0.1897903
>
> Since I am trying to use design matrix to predict after that glmm  
> fitting, could you tell me if there is some function/command that I  
> can use to find what the three "bs" did to my "monthElapsed" variable?
>

As Vito mentioned you probably need a few more knots, see the help on  
bs. The spline models I have fitted have been in lme and have used  
predict to obtain the shape of the curves, but this doesn't seem  
available in lmer.

Ken