Hey everyone, I'm new to Stata and have a question.

I need to aggregate the data by year and company. With the collapse function, I can only sum up the values for the companies for all years.




The raw data look like this:

id year companyid sales
1 2010 555 50,000
2 2010 555 46,000
3 2010 555 40,000
4 2011 555 30,000
5 2011 555 51,000
6 2010 700 2,000
7 2010 700 4,000
8 2011 700 7,000
9 2011 700 11,000
10 2011 700 5,000
.....


The result I need, should look like this:

year companyid Sum
2010 555 136,000
2010 700 6,000
2011 555 81,000
2011 700 23,000
.....


I appreciate any thoughts, many thanks!