Generate a lead variable in a panel

[Musah Khalid]

Cross-posted on stack overflow.


I need help in generating a lead variable in a panel. I want to generate a lead income variable (let's call it V1) by CMA, Province and Year such that the data looks like;

CMA Province Year Income V1
TO A 1990 $5 $8
TO A 1991 $8 .
MT A 1990 $12 $7
MT A 1991 $7 .
AB B 1990 $5 $15
AB B 1990 $15 .
etc

I was using the following codes, but I was getting only missing values.

gsort CMA Province -Year Income
gen ld_inc = Income[_n-1] if Year == Year[_n-1] + 1
replace ld_inc = ld_inc[_n-1] if Year == Year[_n-1] & missing(ld_inc)

Is there something wrong with my code and what I am getting wrong? Thanks in advance.

[Andrew Musau]

Review the FAQs on the top left-hand side of the page for guidance on how to present example data using the dataex command. Stata has time-series operators that are suited for this purpose.

* Example generated by -dataex-. To install: ssc install dataex
clear
input str3(CMA Province) float(Year Income V1)
"TO" "A" 1990  5  8
"TO" "A" 1991  8  .
"MT" "A" 1990 12  7
"MT" "A" 1991  7  .
"AB" "B" 1990  5 15
"AB" "B" 1991 15  .
end

egen id= group(CMA Province), label
xtset id Year
gen wanted = F.Income
assert wanted==V1