Hi @jessegrabowski! Thank you very much for your response.
I missed quite some context, and, unfortunately (for me), it is not a missing data problem. Y is stable isotope data from biological tissue. In short, stable isotopes give information regarding what an animal ate (and where) three months (in my case) before sampling. For example, let’s say that I sampled 20 animals in one year during May. I’d get information about the animal’s behavior from March through May.
Moreover, my animals are pretty mobile, so getting environmental information from where they were sampled would not give enough information in space or time. For this reason, Xs are data from regional oceanographic variables extracted from three-month composite satellite images. That is to say, the only dimension that X and Y share is time.