Thank you for the reply! Now I need to change data 1 to a different dataset. I need to keep observations of days of 0, 7, 14, 21, all the way to 91(name the new variable DAYS2 if not TIME). it is not about rounding of days, I have to use the lab values (INR) in DAYS closest to but not greater than DAYS2 for each DAYS2(0, 7, 14, 21, ~ 91) in the new dataset. For example, the lab values for days2 7 are the values on days 7. If there were no lab values on days 7, chose lab values on days 6. If there were no lab values on days 6, chose lab values on days 5, and so son. Example of the new dataset is given as data3.
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