For my master thesis I have to analyze a large set of longitudinal data, where company data is remeasured every year. Within these data, not all companies have the same number of measurements, which makes the data unbalanced.

Since longitudinal data comes with dependence within-subject, I cannot use normal OLS regressions. Therefore, I was thinking of doing mixed effect linear and logistic regressions.

However, for my additional analysis I was planning to perform a quantile regression. The problem now is that because of the longitudinal data I will have to do a mixed effect quantile regression, of which I have no idea how it works.

My question to you is whether anyone of you perhaps has some experience with this test, and could enlighten me as for how to best approach this?

Thank you in advance!