Filter Specific Data in Stata

Question

I'm using Stata 13 and have to clean a data set in a panel format with different ids for a given period from 2000 to 2003. My data looks like:

id   year    ln_wage
1    2000     2.30
1    2001     2.31
1    2002     2.31
2    2001     1.89
2    2002     1.89
2    2003     2.10
3    2002     1.60
4    2002     2.46
4    2003     2.47
5    2000     2.10
5    2001     2.10
5    2003     2.12

I would like to keep in my dataset for each year only individuals that appear in t-1 year. In this way, the first year of my sample (2000) will be dropped. I'm looking for output like:

2001:

id   year    ln_wage
1    2001     2.31
5    2001     2.10

2002:

   id   year    ln_wage
    1    2002     2.31
    2    2002     1.89

2003:

    id   year        ln_wage
    2    2003     2.10
    4    2003     2.47

Regards,

Wouter Wouter · Accepted Answer · 2021-01-18T06:56:56

* Example generated by -dataex-. To install: ssc install dataex
clear
input byte id int year float ln_wage
1 2000  2.3
1 2001 2.31
1 2002 2.31
2 2001 1.89
2 2002 1.89
2 2003  2.1
3 2002  1.6
4 2002 2.46
4 2003 2.47
5 2000  2.1
5 2001  2.1
5 2003 2.12
end

xtset id year
drop if missing(L.ln_wage)
sort year id
list, noobs sepby(year)

  +---------------------+
  | id   year   ln_wage |
  |---------------------|
  |  1   2001      2.31 |
  |  5   2001       2.1 |
  |---------------------|
  |  1   2002      2.31 |
  |  2   2002      1.89 |
  |---------------------|
  |  2   2003       2.1 |
  |  4   2003      2.47 |
  +---------------------+

// Alternatively, assuming no duplicate years within id exist
bysort id (year): gen todrop = year[_n-1] != year - 1
drop if todrop

Filter Specific Data in Stata

1 Answers