Hello, Below is a small sample of a large data set. Firmid year segmentID segmentsales siccode 1001 1999 1 20 4100 1001 1999 2 10 4200 1001 2000 1 15 4100 1001 2000 2 12 4200 1001 2000 3 13 5100 1002 1999 1 20 4100 1002 1999 2 13 9100 1002 2001 1 20 2867 1002 2001 2 13 3200 1002 2000 3 20 7100 1. First, I can compute how many unique siccode my data has, in this small example above, I have 7 unique siccode 2. my vector will have 7 elements, each element correspond to the segmentsales, for each firm-year, there are non-zero segmentsales and zero segmentsales (when the firm does not have such a segment), e.g. firmid=1001, year=1999, my vector =[20,10,0,0,0,0,0], firmid=1001, year=2000, my vector =[15,12,13,0,0,0] How should I program this? Thanks! Lan
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