Hello all, The ture data has many categories(mor than 400). I want the result to show the rolling 3years std by treatment, but each treatment has different starting points. Now assuming two treatments, could you do me a great favor to get the result as follows(either one is fine)? Thanks a lot. data have; infile cards dlm=',' truncover; input treatment year x; cards; 1,1980,0 1,1981,0 1,1982,0 1,1983,0 1,1984,5 1,1985,7 1,1986,0 1,1987,6 1,1988,2 1,1989,1 2,1980,0 2,1981,0 2,1982,0 2,1983,3 2,1984,4 2,1985,6 2,1986,0 2,1987,7 2,1988,3 2,1989,2 2,1990,1 2,1991,1; run; I hope the result like this: treatment year x std3yr 1 1980 0 . 1 1981 0 . 1 1982 0 . 1 1983 0 . 1 1984 5 . 1 1985 7 . 1 1986 0 3.6055512755 1 1987 6 3.7859388972 1 1988 2 3.0550504633 1 1989 1 2.6457513111 2 1980 0 . 2 1981 0 . 2 1982 0 . 2 1983 3 . 2 1984 4 . 2 1985 6 1.5275252317 2 1986 0 3.0550504633 2 1987 7 3.7859388972 2 1988 3 3.5118845843 2 1989 2 2.6457513111 2 1990 1 1 2 1991 1 0.5773502692 Or treatment year x std3yr 1 1986 0 3.6055512755 1 1987 6 3.7859388972 1 1988 2 3.0550504633 1 1989 1 2.6457513111 2 1985 6 1.5275252317 2 1986 0 3.0550504633 2 1987 7 3.7859388972 2 1988 3 3.5118845843 2 1989 2 2.6457513111 2 1990 1 1 2 1991 1 0.5773502692
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