[R] different DF in package nlme and lme4
Christoph Buser
buser at stat.math.ethz.ch
Mon Jan 3 12:18:18 CET 2005
Hi all
I tried to reproduce an example with lme and used the Orthodont
dataset.
library(nlme)
fm2a.1 <- lme(distance ~ age + Sex, data = Orthodont, random = ~ 1 | Subject)
anova(fm2a.1)
> numDF denDF F-value p-value
> (Intercept) 1 80 4123.156 <.0001
> age 1 80 114.838 <.0001
> Sex 1 25 9.292 0.0054
or alternatively (to get the same result)
fm2a.2 <- lme(distance ~ age + Sex, data = Orthodont, random = list(Subject = ~ 1))
anova(fm2a.2)
> numDF denDF F-value p-value
> (Intercept) 1 80 4123.156 <.0001
> age 1 80 114.838 <.0001
> Sex 1 25 9.292 0.0054
---------------------------------------------------------------
Then I restarted!!! R to use the lme4 package instead of nlme.
---------------------------------------------------------------
library(lme4)
fm2b.1 <- lme(distance ~ age + Sex, data = Orthodont, random = ~ 1 | Subject)
anova(fm2b.1)
> Analysis of Variance Table
> Df Sum Sq Mean Sq Denom F value Pr(>F)
> age 1 235.356 235.356 105.000 114.8383 < 2.2e-16 ***
> Sex 1 19.044 19.044 105.000 9.2921 0.002912 **
or alternatively (to get the same result)
fm2b.2 <- lme(distance ~ age + Sex, data = Orthodont, random = list(Subject = ~ 1anova(fm2b.2)
> Analysis of Variance Table
> Df Sum Sq Mean Sq Denom F value Pr(>F)
> age 1 235.356 235.356 105.000 114.8383 < 2.2e-16 ***
> Sex 1 19.044 19.044 105.000 9.2921 0.002912 **
I got different DF for the denominator. Do I have to use lme in
another way in the package lme4?
I use R 2.0.1 under linux and
Package: nlme
Version: 3.1-53
Date: 2004-11-03
Package: lme4
Version: 0.6-11
Date: 2004-12-16
Thanks for help.
Regards,
Christoph Buser
--
Christoph Buser <buser at stat.math.ethz.ch>
Seminar fuer Statistik, LEO C11
ETH (Federal Inst. Technology) 8092 Zurich SWITZERLAND
phone: x-41-1-632-5414 fax: 632-1228
http://stat.ethz.ch/~buser/
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