[R ] Query : problems with the arithmetic operator "^" with function "lme" and "lmList"
Dear all,
I've got a problem in including square variables in lme and lmlist
functions. I've tried to work on Oxboys data of Pinheiro and
Bates'book, which consist of the heights of 26 boys, each mesured on
nine different occasions :
> Oxboys
Grouped Data: height ~ age | Subject
Subject age height Occasion
1 1 -1.0000 140.50 1
2 1 -0.7479 143.40 2
3 1 -0.4630 144.80 3
4 1 -0.1643 147.10 4
5 1 -0.0027 147.70 5
...
A quadratic model in "age" would be fit with lmList
(height~age+age^2,Oxboys).
We obtain:
fm2Oxboys.lis<-lmList(height~age+age^2,Oxboys) fm2Oxboys.lis
Call: Model: height ~ age + age^2 | Subject Data: Oxboys Coefficients: (Intercept) age 10 130.2616 3.722915 26 137.9927 5.588783 25 139.2105 4.024081 9 138.1369 6.009057 2 142.8584 5.440176 ... 19 164.5761 9.065620 4 165.0724 9.360561 Degrees of freedom: 234 total; 182 residual Residual standard error: 0.6598878 They are not coefficients associated with the covariate "age^2" ! However, the model called is " Height~age+age^2 | Subject " . I would be grateful if anyone could help me. Cordially, Martin Ludovic.