I'm having a problem setting my data for a survival analysis.

I am using STATA 16.0 for windows.

I want to left censor the data so that AdultID is left censored if they appear in the first period. BUT.... here is the hard part for me, i want that AdultID to remain in the dataset if they miss a period or two, but then appear again later. So i want to remove their first 'spell' in the data set, but keep them in for any subsequent 'spells'. I assume i will need to do some sort of loop command.

For example for this AdultID, they appear in period 1 and 2, 7and8, and 19and20. I only want to drop the first spell where they appear in the first and second month because i do not know how many months they were in prior to the first month of my dataset.

AdultID period firstmonth lastmonth
AA19445C 1 1 20
AA19445C 2 1 20
AA19445C 7 1 20
AA19445C 8 1 20
AA19445C 19 1 20
AA19445C 20 1 20


Here is a sample of my data....

.
. dataex AdultID period firstmonth lastmonth

----------------------- copy starting from the next line -----------------------
Code:
* Example generated by -dataex-. To install: ssc install dataex
clear
input str8 AdultID float(period firstmonth lastmonth)
"AA000J5L"  1  1 22
"AA000J5L"  2  1 22
"AA000J5L"  3  1 22
"AA000J5L"  4  1 22
"AA000J5L"  5  1 22
"AA000J5L"  6  1 22
"AA000J5L"  7  1 22
"AA000J5L"  8  1 22
"AA000J5L"  9  1 22
"AA000J5L" 10  1 22
"AA000J5L" 11  1 22
"AA000J5L" 12  1 22
"AA000J5L" 13  1 22
"AA000J5L" 14  1 22
"AA000J5L" 15  1 22
"AA000J5L" 16  1 22
"AA000J5L" 17  1 22
"AA000J5L" 18  1 22
"AA000J5L" 19  1 22
"AA000J5L" 20  1 22
"AA000J5L" 21  1 22
"AA000J5L" 22  1 22
"AA03597B" 20 20 24
"AA03597B" 21 20 24
"AA03597B" 22 20 24
"AA03597B" 23 20 24
"AA03597B" 24 20 24
"AA05469D"  9  9 11
"AA05469D" 11  9 11
"AA05568B"  1  1 24
"AA05568B"  2  1 24
"AA05568B"  3  1 24
"AA05568B"  4  1 24
"AA05568B"  5  1 24
"AA05568B"  6  1 24
"AA05568B"  7  1 24
"AA05568B"  8  1 24
"AA05568B"  9  1 24
"AA05568B" 10  1 24
"AA05568B" 11  1 24
"AA05568B" 12  1 24
"AA05568B" 13  1 24
"AA05568B" 14  1 24
"AA05568B" 15  1 24
"AA05568B" 16  1 24
"AA05568B" 17  1 24
"AA05568B" 18  1 24
"AA05568B" 19  1 24
"AA05568B" 20  1 24
"AA05568B" 21  1 24
"AA05568B" 22  1 24
"AA05568B" 23  1 24
"AA05568B" 24  1 24
"AA05824D"  1  1  9
"AA05824D"  2  1  9
"AA05824D"  3  1  9
"AA05824D"  4  1  9
"AA05824D"  5  1  9
"AA05824D"  6  1  9
"AA05824D"  7  1  9
"AA05824D"  8  1  9
"AA05824D"  9  1  9
"AA07275F" 14 14 24
"AA07275F" 15 14 24
"AA07275F" 16 14 24
"AA07275F" 17 14 24
"AA07275F" 19 14 24
"AA07275F" 20 14 24
"AA07275F" 21 14 24
"AA07275F" 22 14 24
"AA07275F" 23 14 24
"AA07275F" 24 14 24
"AA10840J"  3  3 11
"AA10840J"  4  3 11
"AA10840J"  6  3 11
"AA10840J"  7  3 11
"AA10840J"  8  3 11
"AA10840J"  9  3 11
"AA10840J" 10  3 11
"AA10840J" 11  3 11
"AA11244G"  2  2 24
"AA11244G"  3  2 24
"AA11244G"  4  2 24
"AA11244G"  5  2 24
"AA11244G"  6  2 24
"AA11244G"  7  2 24
"AA11244G"  8  2 24
"AA11244G"  9  2 24
"AA11244G" 10  2 24
"AA11244G" 11  2 24
"AA11244G" 12  2 24
"AA11244G" 13  2 24
"AA11244G" 14  2 24
"AA11244G" 15  2 24
"AA11244G" 16  2 24
"AA11244G" 17  2 24
"AA11244G" 18  2 24
"AA11244G" 19  2 24
"AA11244G" 20  2 24
"AA11244G" 21  2 24
end
------------------ copy up to and including the previous line ------------------

Listed 100 out of 189543 observations
Use the count() option to list more