Generating start and stop time variables

[Buyadaa Oyunchimeg]

Dear Stata users,

I wonder if there is an easy way to generate 'start' and 'stop' days from baseline from using long format data.

Dataex:

----------------------- copy starting from the next line -----------------------
[CODE]
* Example generated by -dataex-. For more info, type help dataex
clear
input byte id str9(medication days_from_baseline) byte event
3 "D-penicil" "0"         0
3 "D-penicil" ".48187494" 0
3 "D-penicil" ".99660498" 0
3 "D-penicil" "2.0342789" 0
3 "D-penicil" "2.7707808" 1
5 "placebo"   "0"         0
5 "placebo"   ".54484725" 0
5 "placebo"   "1.070529"  0
5 "placebo"   "2.1054649" 0
5 "placebo"   "3.0062425" 0
5 "placebo"   "3.9836819" 0
5 "placebo"   "4.1205783" 0
end
[/CODE]
------------------ copy up to and including the previous line ------------------ 

I would like to create the following data.

id medication   start         stop    event
3 D-penicil   0          .48187494  0
3 D-penicil   .48187494  .99660498  0
3 D-penicil   .99660498 2.0342789   0   
3 D-penicil  2.0342789  2.7707808   1
5 placebo   0            .54484725  0
5 placebo    .54484725  1.070529    0
5 placebo   1.070529    2.1054649   0
5 placebo   2.1054649   3.0062425   0
5 placebo   3.0062425   3.9836819   0
5 placebo   3.9836819   4.1205783   0 

Many thanks,
Oyun

[Nick Cox]

destring start, replace 

bysort id (start) : gen stop = start[_n+1] 

by id : drop if _n == _N 

bysort id (start): replace event = 1 if _n == _N

However, why is start string in the first place? See #8 in https://www.statalist.org/forums/for...ing-a-variable for some of the reasons why a variable that should be numeric has been created as string.

It is a small point but please use CODE delimiters (# button in the forum interface), not PHP Code delimiters.

[Buyadaa Oyunchimeg]

Thanks very much Nick.
It seems that something went wrong with 'start'. My apologies for the inconvenience. I will use CODE delimiters in the future.