[R] degrees of freedom in a LME model

[Federico Calboli]

Dear All,

I am analysing some data for a colleague (not my data, gotta be published
so I cannot divulge).

My response variable is the number of matings observed per day for some
fruitlies.

My factors are:
Day: the observations were taken on 9 days
Regime: 3 selection regimes
Line: 3 replicates per selection regime.

I have 81 observations in total

The lines are coded A to I, so I do not need to do any extra grouping.

my model is:

anova(lme(Matings ~ Day * Regime, random = ~1| Line/Day, mydata))

I would expect to have:
1 df per Day
2 df per Regime
2 df per Day * Regime
6 df per Line %in% Regime
6 df per Day * Line %in% Regime,


so my anova would have:

	numDF	denDF
int	1	63
Day	1	6
Regime	2	6
D*R	2	6

what I get is:

	numDF	denDF
int	1	69
Day	1	69
Regime	2	6
D*R	2	69

why is lme not calculating correctly the Line/Day interation ?

I am using R 1.7.0 under W2K, although I updated the packages and I get the
warning "nlme lib built under R1.7.1..."

Regards,

Federico 


=========================

Federico C.F. Calboli

Department of Biology
University College London
Room 327
Darwin Building
Gower Street
London
WClE 6BT

Tel: (+44) 020 7679 4395 
Fax (+44) 020 7679 7096
f.calboli at ucl.ac.uk