Hi all,

Im new to STATA so I apologise if this is a silly question. I am trying to combine two datasets; these datasets represent two waves of data (time 1 & time 3). I've used the following code:


*import excel dataset
import excel "/Users/bridget/Dropbox/PhD/Data/T1.xlsx", sheet("Sheet1") firstrow clear

*save dataset as dta
save T1.dta

*import excel dataset
import excel "/Users/bridget/Dropbox/PhD/Data/T3.xlsx", sheet("Sheet1") firstrow clear

*save dataset as dta
save T3.dta

*merge datasets
merge 1:1 ID using T1.dta, generate(_mergeT1)
merge 1:1 ID using T3.dta, generate(_mergeT3)
save MERGED.dta


However, I get the following error message:

"variable ID does not uniquely identify observations in the master data
r(459)"


Any guidance on this would be greatly appreciated!!