Dear Statalisters,

I am working with a longitudinal dataset. I'm trying to create a variable to capture change between two periods in one variable, but only when a different variable remains constant.

Essentially, my goal is to create a single row for each "wave" by creating a new variable that will represent a specific change in the said variable, and then delete the left-over row for that year.

Code:
* Example generated by -dataex-. To install: ssc install dataex
clear
input long id_num byte(wave jobcens)
101  1 3
101  2 1
101  3 1
101  5 2
101  5 3
101  6 2
101  8 3
101  9 1
101 10 2
101 10 3
101 11 1

end

From the above code, the cases below represent the type of cases I mean to capture and what I'd like them to be (6, in this case):

101 5 2
101 5 3 --> 101 5 6

101 10 2
101 10 3 --> 101 10 6


I've used the following code in the past to create a change variable:

gen change_var = .

replace change_var = 6 if x1[_n-1] == 1 & x1 == 2 & id_num[_n-1] == id_num

However, the added stipulation I face is to restrict this to only happen when the "wave" is the same. I'm wondering if I will need to turn the dataset wide to do this? And if so, any suggestions on how might I do still achieve the same goal?

Thank you in advance!

Much appreciation,
Wyatt