I was wondering if someone can help me figure out the following:
I have two patient datasets, ds1 and ds2. ds1 has fields "patid", "date",
and "lab1". ds2 has "patid", "date", and "lab2". I want to find all the
patids that have at least 2 dated records for each lab. I started by
splitting each dataset by patid, to create ds1.list and ds2.list. Then I
did some processing (with sapply) to each list to get the lengths of each
patient list item. Then I kind of lost my way and things got messy as I
tried to extract just the patids of those with lengths >= 2, convert them
to dataframes (which I didn't have much success with), and then merge the
two dataframes to get a vector of the desired patids. Any help would be
much appreciated.
Thanks,
Steven