Dear All, I am working on a project for which I have to get mean levels of a disease marker (let's call it DM). The issue is that the mean must only include measures before the individual developed disease, and the time each person may have developed disease differs. So, for example, if ID=1 has 7 time points where DM was assessed and this person developed disease at time 5, I would need the mean of DM from time 1 to time 4. If ID=2 has DM measured from time 1 to 6 and the person developed disease at time 3, I'd need the mean DM from time 1 to time 2. If another person did not develop disease, I'd get the mean of all the available DM measures. I am really stuck on how to do this. Any help would be greatly appreciated! Many thanks!
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