Help Command to generate a new variable

[Josh Wang]

Hello, here is a part of the data of the firms with different id.
I'd like to generate a new variable that equals the current year if the firm first time has positiv revenue.
For example, firm id =2 first time has a positive revenue in 2012, the the NewVar=2012 for firm id= 2.
I manually generate the NewVar to help you to understand what I want.
Thanks for the help!

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* Example generated by -dataex-. For more info, type help dataex
clear
input byte id int(revenue year NewVar)
1 100 2010 2010
1  98 2011 2010
1 103 2012 2010
1 110 2013 2010
1 106 2014 2010
1 107 2015 2010
2   0 2011 2012
2  95 2012 2012
2   0 2013 2012
2  99 2014 2012
2  98 2015 2012
3  80 2013 2013
3  90 2014 2013
3 100 2015 2013
4   0 2010 2011
4  79 2011 2011
4  89 2012 2011
4  97 2013 2011
5   0 2010    .
5   0 1011    .
5   0 2012    .
5   0 2013    .
end

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[Hemanshu Kumar]

Try this:

bysort id: egen int wanted = min(cond(revenue>0,year,.))
assert wanted == NewVar