Hello,

input hid day_bought min_day str20 product str20 manufacturer

hid day_bought min_day product manufacturer
1. 1 10 5 "A" "a"
2. 1 8 5 "A" "a"
3. 1 5 5 "A" "a"
4. 1 7 7 "B" "a"
5. 1 8 7 "B" "a"
6. 1 11 11 "C" "c"
7. 1 12 11 "C" "c"
8. 2 12 9 "A" "a"
9. 2 9 9 "A" "a"
10. 2 11 3 "C" "c"
11. 2 3 3 "C" "c"
12. 2 4 3 "C" "c"
13. 3 4 2 "B" "a"
14. 3 2 2 "B" "a"
15. 4 19 2 "A" "a"
16. 4 15 2 "A" "a"
17. 4 2 2 "A" "a"
18. 4 16 16 "B" "a"
19. 4 18 16 "B" "a"
20. end

I am trying to compute a few descriptive variables. First, a "manufexp" variable which counts how many time was the household (hid) exposed to a product of the same manufacturer (that isn't the same product). Here's an example for what this new variable should look like

manufex~y
1. 0
2. 0
3. 0
4. 1
5. 1
6. 0
7. 0
8. 0
9. 0
10. 0
11. 0
12. 0
13. 0
14. 0
15. 1
16. 0
17. 0
18. 1
19. 1

Which mentions in this example purchase 4. and 5., since household 1 was exposed to manufacturer "1" through his purchase 3. and purchase 15., since household 4 was exposed to manufacturer "a" by day 19 through purchase 19 and also 18 and 19 since he was exposed to manufacturer "a" when purchasing "B" through purchase 16.
Second, I want a variable which mentions the number of exposures to the same manufacturers before each fist purchase for all products (the manufexp) to be the same for every household and every product (just like min_day is the same min_day).

I tried this
bysort hid prod: egen manufexp = count(manufacturer) if day_bought<min
and it doesn't work as I get only missing values everywhere.

Thank you very much in advance,
Sincerely,
SA