# Crossed random effects - Beyond NLME; The orange data revisited
ADMB Files
Code: orange2.tpl Data: orange2.dat Initial values: orange2.pin All required files (DOS): orange2.zip All required files (linux): orange2.tar.gz Results: orange2.par
Running ADMB-executables
In a DOS window Under linux
Navigation
ADMB-RE home Otter Research
| ### Model description The orange data were considered by Millar (2004, Aust NZ J. Stat, 46, p. 543-554). A "day effect" (v) was added to the original model formulation, yielding yij = f1,ij /(1 + exp[-(t-f2)/f3]) ] + eij, f1,ij = f1 + ui + vj where u is a tree-effect and v is a day-effect. This is an example of a model where the random effects u and v are crossed. Such models cannot easily be fit in `nlme` (Pinheiro & Bates, 2000), while the inclusion of the random effect v requires only 2-3 lines of extra code in the ADMB-RE program. ### Comparison with Millar (2004) Millar (2004) used simulated likelihood to evaluate the marginal likelihood. The following table shows a comparison of point estimates and standard deviations (SD):
| Millar | SD | ADMB-RE | SD
f1 | 195.9 | 14.5 | 196.2 | 19.4
f2 | 747.6 | 59.1 | 748.4 | 62.3
f3 | 352.7 | 32.0 | 352.9 | 33.3
Var(e | 28.1 | 8.2 | 28.1 | 8.2
Var(u) | 1059.8 | 684.5 | 1061.0 | 687.6
Var(v) | 109.1 | 88.8 | 109.9 | 90.7
The differences between the two approaches are minor.