Create year variable

[Baltazar Loewe]

Dear Statalists,

I have seen the following line in someone else's code and I am not sure I understand what is done here. I suspect that it aims to create the year from the monthly date_m. Can you tell me whether this is the proper way to achieve this transformation?

gen year = 1960 + floor(date_m/12)

I would very much appreciate your feedback on this!

Best,
Baltazar

[Andrew Musau]

If you have monthly dates starting from 0 and zero represents the first month of the year, then months 0-11 are in year 1, months 12-23 are in year 2, and so on.

display floor(0/12)
display floor(7/12)
display floor(11/12)
display floor(12/12)
display floor(23/12)
display floor(24/12)

Res.:

. display floor(0/12)
0

. display floor(7/12)
0

. display floor(11/12)
0

. display floor(12/12)
1

. display floor(23/12)
1

. display floor(24/12)
2

So if the author knows that month 0 is January 1960, he/she can recreate the year variable by adding 1960 to the floor of monthly date divided by 12.

[Maarten Buis]

Andrew is right that this won't work for Stata's monthly date, as it counts the months from 1 to 12 and not 0 to 11. Instead I would use the Stata functions for dealing with times, see help datetime.

gen year = year(dofm(date_m))

[Baltazar Loewe]

Thank you Andrew Musau and Maarten Buis for your quick and competent reply! This is very helpful.