Random effects models of the type fitted by ordinal assume something akin to compound symmetry, which is not realistic when time between measurements is long or irregular. Frank Rune Haubo-2 wrote
lmer is not designed for ordered categorical data as yours are. You could take a look at the ordinal package which is designed for this type of data including mixed models (function clmm) which you probably want to use. Best, Rune Den 24/03/2011 21.03 skrev "Rasanga Ruwanthi" <
ruwanthi_kdr@
>:
Dear List, I have some longitudinal data, each patient was followed at times 0, 12,
16, 24 weeks and measure severity of a illness (0-worse, 1-same, 2-better). So, longitudinal response is categorical. I was wondering whether lmer in R can fit a model for this type of data. If so, how we code? Or any other function in R that can fit this type of longitudinal data? Any suggestion would be greatly appreciated.
Thanks
Ruwanthi
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