Months since a var=1

[Collin James]

Months s

[Collin James]

Hello, sorry, I hit post too soon. So, I have a variable that=1 if someone has a call in a certain month year (it is called ref_this_month). Example below--data is at month-year-person level (mci is person id). I want to create a variable that counts how many months from the FIRST time ref_this_month=1 for a person. So, for instance, for the ID below, the first observation for 526 would show a -1 (since 2018 m1 is 1 month before he gets a ref_this_month==1) and 2018 m3 observation would equal 1. However, there may be more than one ref_this_month==1 and I want it to only count from the first instance this occurs.Thanks -CJ

* Example generated by -dataex-. For more info, type help dataex
clear
input long mci float(month yr ref_this_month)
526  1 2018 0
526  2 2018 1
526  3 2018 0
526  4 2018 0
526  5 2018 0
end

[Clyde Schechter]

//  FIRST CREATE A STATA INTERNAL FORMAT MONTHLY DATE VARIABLE
gen int mdate = ym(yr, month)
format mdate %tm

//  IDENTIFY MONTH OF FIRST REFERENCE
by mci (mdate), sort: egen int month_first_ref = min(cond(ref_this_month, mdate, .))
format month_first_ref %tm

//  CALCULATE TIME TO OR SINCE MONTH FIRST REF
gen wanted = mdate - month_first_ref

[Collin James]

Thank you CLyde!