Linking two datasets with unique identifiers with multiple observations using frames

[Kim Tang]

Hi all, I have two data sets the first: unique identifiers sending in scores and each person can send scores at different times; second data set: unique identifiers being hospitalized or visit the ER which can be multiple times. I want to link the two data sets using frames and their unique identifier

If tried this code:

use Hospitalizations.dta
frame rename default Hospitalizations
frame create scores
frame scores: use scores.dta

sort UniqueIdentifier

frlink m:1 UniqueIdentifier, frame (scores)

THEN, I get the error message "invalid match variables for 1:1 or m:1 match. The variable you specified for matching does not uniquely identify observations in frame scores. Each observation in the current frame Hospitalizations must link to one observation in scores"