variable id does not uniquely identify observations in the using data

[Marie Sofie]

Dear All,

I have two datasets. First collected from 600 people (wave 1), which was intended to measure some baseline attitudes, and then after that a sub-sample of these subjects were randomly assigned to treatment groups (wave 2), n=130. Now I am trying to merge the wave 1 data with the wave 2 data. Both of them have the variable ID number, and the merge should be matched with ID numbers. But everytime I try the following:

merge m:1 id using "C:\Users\U0114841\Desktop\dataforoxfordultimate\w ave_1_ultimate_dataset_clean.dta"

I get the below message:
variable id does not uniquely identify observations in the using data

I have no idea why. I would appreciate so much if you could help me out with this.

Thanks a lot.

Best,

Marie Sofie

[Brian Brosmer]

use "C:\Users\U0114841\Desktop\dataforoxfordultimate\w ave_1_ultimate_dataset_clean.dta", clear
duplicates examples id

[Dimitriy V. Masterov]

This sounds like a 1:1 merge, not m:1, but that is not what is breaking the code. I would open each file and check to see if id has any duplicates:

isid id

The -duplicates- command will be useful if that check fails.

[Marie Sofie]

It is fabulous! Thanks a million for these advices. It does indeed work now, after I have cleaned up the duplicates.