Is it possible to merge multiple observations into one observation based on ID and a categorical variable? Right now I have multiple observations for each record when I only need one observation per record ID for each level of a categorical variable, this is what I need to do:   Record ID:          Category:          Record ID (grouped):          Category (grouped): 1                                2                                 1                                        2 1                                2 1                                3                                 1                                        3 1                                3 1                                3 2                                4                                 2                                        4 2                                4   How do I take the first two columns and group them to create the second two columns? ... View more

I am trying to pull in longitudinal data, and keep those with greater than 3 observations. I am using a first. last. statement to keep IDs and create an observation counter to ensure that I am keeping only those with greater than 3 observations. When I do this, the last observation is kept, and when I try to merge this back into the data set, the first observation is overwritten by the last observation being pulled from the first. last. How do I keep the first observation or at least avoid overwriting? Here is the code I am using:   DATA UniqueID; SET Dementia; BY ID Age; IF First.ID = 1 THEN OBSCNT = 0; OBSCNT + 1; IF Last.ID = 1 AND OBSCNT GE 3; RUN; ... View more