Hello Statalist contributors,

I am looking for a solution to a problem that seems unanswered on this forum as of now even if there are people asking similar questions.

I have 42 blood biomarkers and it is common practice to reduce those to a smaller number of factors to understand the data. I therefore would conduct a PCA on it and go from there but in this particular case, I have two sets of these data on the same participants with 3 months apart. I would like to compare PCA's but of course I cannot simply conduct a PCA at each time point and compare them so the question is, are there known methods for conducting and comparing PCA's from two time points? I have found that there is a program called Multiple Factorial Analysis in R and an article on the subject but sadly I am simply inept in R. Is there something equivalent in Stata?

Any advice would be greatly appreciated.

J-M