[R] How to test combined effects?

[Dieter Menne]

Gang Chen <gangchen <at> mail.nih.gov> writes:

> 
> Suppose I have a mixed-effects model where yij is the jth sample for  
> the ith subject:
> 
> yij= beta0 + beta1(age) + beta2(age^2) + beta3(age^3) + beta4(IQ) +   
> beta5(IQ^2) + beta6(age*IQ)  + beta7(age^2*IQ)  +  beta8(age^3 *IQ)  
> +random intercepti + eij
> 
> In R how can I get an F test against the null hypothesis of  
> beta6=beta7=beta8=0? In SAS I can run something like contrast  age*IQ  
> 1, age^2*IQ 1, age^3 *IQ 1, but is there anything similar in R?

Check packages multcomp and gmodels for contrast tests that work with lme.

Dieter