[R ] Query : problems with the arithmetic operator "^" with function "lme" and "lmList"
Hello, Check also function "AsIs" ( Usage: I(x) ). Regards, Carlos. -----Mensaje original----- De: r-help-bounces at stat.math.ethz.ch [mailto:r-help-bounces at stat.math.ethz.ch] En nombre de Bashir Saghir (Aztek Global) Enviado el: mi?rcoles, 07 de mayo de 2003 14:33 Para: 'MARTIN Ludovic' CC: 'r-help at stat.math.ethz.ch' Asunto: RE: [R] [R ] Query : problems with the arithmetic operator "^" with function "lme" and "lmList" Dear Martin, Have you try to create a new variable for age squared, say agesq? If you fit the model using this new variable you should get the coefficients. So your new model is something like height~age+agesq I hope this helps, Saghir
-----Original Message----- From: MARTIN Ludovic [SMTP:martinl at mathinfo.ens.univ-reims.fr] Sent: Wednesday, 07 May, 2003 2:02 PM To: r-help at stat.math.ethz.ch Subject: [R] [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.
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