Dear All,
I've come across a problem in predict.lme. Assigning a model formula to a
variable and then using this variable in lme (instead of typing the formula into
the formula part of lme) works as expect. However, when performing a predict on
the fitted model I gan an error messag - predict.lme (but not predictlm) seems
to expect a 'properly' typed in formula and a cannot extract the formula
from the variable. THe code below demonstrates this.
Is this a known or expected behavour of predict.lme or is this a bug?
kind regards,
Arne
(R-2.1.0)> library(nlme)
...> mod <- distance ~ age + Sex # example from ?lme
> mod
distance ~ age + Sex> fm2 <- lme(mod, data = Orthodont, random = ~ 1)
> anova(fm2)
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> fm2
Linear mixed-effects model fit by REML
Data: Orthodont
Log-restricted-likelihood: -218.7563
Fixed: mod
^^^^
...
> predict(fm2, Orthodont)
Error in mCall[["fixed"]][-2] : object is not subsettable
> fm2 <- update(fm2, . ~ .) # this replaces "mod" by the
contents of variable mod
> fm2
Linear mixed-effects model fit by REML
Data: Orthodont
Log-restricted-likelihood: -218.7563
Fixed: distance ~ age + Sex
...
> predict(fm2, Orthodont)
M01 M01 M01 M01 ...
25.39237 26.71274 28.03311 29.35348 21.61052 ...
> fm2 <- lm(mod, data = Orthodont)
> predict(fm2, Orthodont)
1 2 3 4 ...
22.98819 24.30856 25.62894 26.94931 ...
