There are three variables. company_code, year, count. code year count Sum_count 10 2000 1 1 10 2001 . . 10 2002 1 1 10 2002 1 2 10 2003 1 1 10 2003 1 2 10 2003 1 3 20 2000 . . 20 2000 1 1 I wnat know the code how can I make Sum_count variable. Sum_count is the sum of count(by code, year). If you help me I will really appreciate about it. My english is not good. I'm sorry.
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