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From |
Steve Samuels <sjsamuels@gmail.com> |

To |
statalist@hsphsun2.harvard.edu |

Subject |
Re: st: Interval Censored Data Formatting and Intcens |

Date |
Sat, 2 Jun 2012 21:17:39 -0400 |

You are asked in the FAQ to say where you obtained unofficial commands. -intcens- can be downloaded from SSC. You say you want to transfer the structure of your data to Stata, but you don't show that structure, so we have to guess. I'm guessing that your basic data looked something like that after the input statement below ( "wide form"). If not, it might look something like the listed data after the -reshape- command (below), the "long form" If not that either, then you will have to put your data into one of the two forms. For the wide form: let i = 1,3,13, 21 index coses and let statusi = observation just after dose i = 1 if death after dose i = 0 if no death after dose i = . no dose i given *************CODE BEGINS************* input id status1 status3 status13 status21 1 0 1 . . 2 0 0 1 . 3 0 0 0 1 4 0 0 . 1 5 0 . . 0 end reshape long status, i(id) j(dose) drop if status==. list, sepby(id) // long form egen event = max(status), by(id) gen t1 = dose if status==1 bysort id: gen t0 = dose[_n-1] if status==1 bysort id: keep if _n==_N replace t0 = dose if t0==. list id t0 t1 status ***********CODE ENDS*************** This is an interesting application of -intcens-, but two points concern me. 1. You apparently applied 2+ doses to the each subject. If the effect of former dosing persists in any way, then the probability of an event will not depend only on current dose. 2. Dosing in groups could result in dependent responses. I am curious: Can you provide a methodological reference for this design? Steve sjsamuels@gmail.com On Jun 1, 2012, at 5:12 PM, Ciril Bosch-Rosa wrote: Hello, I am trying to apply survival analysis in an environment where I can gather data in a very limited way. I have been looking at literature on how to manage the data but am not being successful at transmitting the structure of my data to Stata. It turns out that my data is very limited because I can only observe once in time each subject. I am taking this as an interval censored problem, where all subjects start being at risk at t_0 and then are censored until I look at some of them at (say) t_13, where they are either 1 (dead) or 0 (right censored). So, either the subject died at some before (and including) t_13 or he survived in which case I will never see him again (hence the right censoring). I looked at Cleves et al. but they are not clear on how I can tell Stata that an even happened while "I was not looking". They tell me how to tell stata I was not looking, but not how to tell I was not looking & something happened: id t_0 t_1 event 1 1 3 0 1 13 15 1 the example above I tell stata there is a censored interval from t=3 until t=13 and then I observe id=1 until he gets a failure at t=15, but I am not able to tell stata that they might have died in the t3-t13 interval: id t_0 t_1 event 1 1 3 0 1 13 13 1 2 1 3 0 2 13 13 0 In other words I observe you from t=1 to t=3 and then you get censored until I get one peek at t=13, where I can see if you died between 3 and 13 or not. I believe this can be done with ""intcens depvar1 depvar2 " where depvar are my t=3 and t=13 respectively, my problem though is that there are different interval censoring for different subjects id t_0 t_1 event 1 1 3 0 1 13 13 1 2 1 3 0 2 13 13 0 3 1 3 0 3 21 21 1 4 1 3 0 4 21 21 1 how can I tell intcens, "intcens depvar1 depvar2 if id=1|2 but depvar1 depvar3 if id=3|4" ?? Any help/advice is welcome Ciril PS If you are wondering in what environment I get this kind of data; this is a lab experiment where I apply a dose to groups of subjects and get instantaneous results, hence my observing groups of them at the same "time". My X-axis is not time, but rather "dosage" and I am trying to plot the survivor curve given the very limited observable outcomes for each dosage. * * For searches and help try: * http://www.stata.com/help.cgi?search * http://www.stata.com/support/statalist/faq * http://www.ats.ucla.edu/stat/stata/ * * For searches and help try: * http://www.stata.com/help.cgi?search * http://www.stata.com/support/statalist/faq * http://www.ats.ucla.edu/stat/stata/

**References**:**st: Interval Censored Data Formatting and Intcens***From:*"Ciril Bosch-Rosa" <cirilbosch@gmail.com>

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