Adding duplicates together

[Patrick Mulcahy]

I have two data sets.

data set a with group level data for variables x, y, and group_id.

data set b with individual level data for variables a, b and group_id. This data has duplicates of group_id. I want to add together var_a if group_id is the same and add together var_b if group_id is the same. To transform individual level data into group level data so I can merge it with data set a.

current data set b

group_id	var_a	var_b
1	100	60
1	50	10
2	30	20
2	10	70
3	110	130

I want it to look like:

group_id	var_a	var_b
1	150	70
2	40	90
3	110	130

I have tried to gen and egen new variables but have not been able to get anything to work. Any code or even the command to look at would be appreciated.

[Justin Niakamal]

collapse (sum) var_* , by (group_id)

[Patrick Mulcahy]

After struggling for too long I got it 10 minutes after posting this.

The code I used is:

egen var_a2=total(var_a), by (group_id)
egen var_b2=total(var_b), by (group_id)
drop var_a
drop var_b