# Is there an R package for continuous time longitudinal binary responses?

The bild package appears to be an excellent package for serial binary responses. But it is for discrete time. I would like to specify a smooth function of time for the odds ratio connection of the current response Y with binary responses measured at earlier times, or at least a first-order Markov version of this. I believe this is called alternating logistic regression. Does anyone know of an R package that handles continuous time, i.e., measurement times can be at any follow-up time? I don't need random effects in the model.

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I haven't used it, but for alternating logistic regression, a quick search turned up this ALR package: hsph.harvard.edu/carey/vcwww_4.html –  pat Oct 22 '12 at 6:06
Thanks for this comment. The best I can tell from the documentation, alr is only for discrete time. –  Frank Harrell Oct 22 '12 at 13:28
The authors programmed the combinatoric calculations by generating a combinatoric dataset, making it not computationally efficient enough for large $N$. They perhaps did that to make it work in SAS IML. In addition, I can't tell if their method has the properties of a full likelihood approach, i.e., whether it is robust to non-random dropout as generalized least squares and mixed effects models are. Their method is akin to the non-full-likelihood alternating logistic regression (ALR), implying you have to use multiple imputation on top of ALR to make the missing values missing at random. –  Frank Harrell Mar 24 '13 at 19:51