Can there be different number of timepoints for Generalized Linear Mixed Model?

[Liz123]

Hello everyone, 

For generalized  linear mixed model analyses, can  there be different number of time points for  each individual or study  participant? I am aware that it accommodates  varying timepoints, but I am not sure about the the number of timepoints. For example, can an individual have  5 timepoints  and another 7 timepoints and another individual 30 timepoints or do they need to have  equal number of timepoints for one to conduct this type of analyses?  Is there a maximum number of timepoints especially for graphical presentation?

Also, can anyone share  resource(s) on how to interpret the SAS Output for  Generalized Linear Mixed Model/ how to report the results? Thank you. 

[Ksharp]

“can an individual have 5 timepoints and another 7 timepoints and another individual 30 timepoints”
Yes. You can have different timepoints within different subject.
But you need specify a variable in REPEAT , like:
repeat time/subject=subject type=ar(1);

https://stats.oarc.ucla.edu/other/mult-pkg/introduction-to-generalized-linear-mixed-models/
https://blogs.sas.com/content/iml/2019/12/03/longitudinal-data-response-profile-model.html
https://blogs.sas.com/content/iml/2019/12/05/longitudinal-data-mixed-model.html

could give you a beginning of Mixed Model.
or @SteveDenham could give you more advices .

[Liz123]

@Ksharp This is great! Thank you so much!

[jiltao]

Yes, the number of time points can be different across subjects. 

I am not aware of a limit on the number of time points in theory, but practically, it might run out of memory if you have too many time points and you use a complex covariance structure such as UN. Graphically too many time points might make the graph hard to reveal anything. But as long as your computer can handle it, you could have as many time points as you wish.

Output interpretations are provided in many examples in the PROC GLIMMIX documentation. For example,

https://go.documentation.sas.com/doc/en/pgmsascdc/v_046/statug/statug_glimmix_gettingstarted01.htm

https://go.documentation.sas.com/doc/en/pgmsascdc/v_046/statug/statug_glimmix_examples.htm

Hope this helps,

Jill

[Liz123]

@jiltao Thank you for this! Highly appreciated!