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From |
"Alex Gamma" <alex.gamma@uzh.ch> |

To |
<statalist@hsphsun2.harvard.edu> |

Subject |
st: sts graph: different results with -atrisk- vs -risktable- option |

Date |
Tue, 12 Apr 2011 14:49:59 +0200 |

Dear Statasticians, I have multiple-record survival-time data and -stset- them as shown further below. There are 30 records for each of 591 subjects. My question: why do I get different numbers at risk with -sts graph-'s -risktable- vs -atrisk- options? With -sts graph, risktable name(risktable, replace)-, I get numbers at risk 192, 169, 102, 0 for analysis time 0, 10, 20, 30 years, respectively. With -sts graph, atrisk name(atrisk, replace)-, I get numbers at risk 960, 382, 361, 338, 166, 328, 524, 232, 536 for the beginnings of each interval. I'm aware that the time points for which the numbers at risk are calculated are not the same for the two options, but what worries me is that -atrisk- produces numbers that are much higher than the number of subjects in the analysis. In fact, for the first time point, the number reported by -atrisk- (960) is exactly the 5-fold of that reported by risktable- (192). The latter number is the right one, since it corresponds to the total number of subjects in the analysis, as shown in the results of -stset-. I've searched the statalist archives, the Stata FAQ, the Stata manual entry for sts graph, and googled "Stata risktable atrisk", but I found nothing that addressed this discrepancy. Further below, I'm also including the results of -sts list-. Maybe they help diagnose the problem. Best regards, Alex . stset year, id(intnr) failure(de43fail==0) origin(de4==3) enter(year==1979) if(!missing(de43nosx3yv)) id: intnr failure event: de43fail == 0 obs. time interval: (year[_n-1], year] enter on or after: year==1979 exit on or before: failure t for analysis: (time-origin) origin: de4==3 if: !missing(de43nosx3yv) ------------------------------------------------------------------------------ 17730 total obs. 11814 ignored per request (if(), etc.) 1744 obs. end on or before origin() 165 obs. begin on or after (first) failure ------------------------------------------------------------------------------ 4007 obs. remaining, representing 192 subjects 67 failures in single failure-per-subject data 4007 total analysis time at risk, at risk from t = 0 earliest observed entry t = 0 last observed exit t = 29 . sts list failure _d: de43fail == 0 analysis time _t: (year-origin) origin: de4==3 enter on or after: year==1979 id: intnr Beg. Net Survivor Time Total Fail Lost Function ------------------------------------------ 5 192 1 0 0.9948 7 191 1 0 0.9896 9 190 4 17 0.9688 11 169 3 0 0.9516 12 166 2 0 0.9401 14 164 1 0 0.9344 15 163 10 22 0.8770 18 131 1 0 0.8703 20 130 9 20 0.8101 22 101 12 18 0.7138 27 71 14 17 0.5731 29 40 9 31 0.4441 ------------------------------------------ -- Alex Gamma Ph.D. University Hospital of Psychiatry Research Department Lenggstr. 31 8032 Zurich Switzerland Tel: +4144 384 2621 Fax: +4144 384 2446 e-mail: alex.gamma@uzh.ch -- Alex Gamma Ph.D. University Hospital of Psychiatry Research Department Lenggstr. 31 8032 Zurich Switzerland Tel: +4144 384 2621 Fax: +4144 384 2446

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**Follow-Ups**:**Re: st: sts graph: different results with -atrisk- vs -risktable- option***From:*Joerg Luedicke <joerg.luedicke@gmail.com>

**Re: st: sts graph: different results with -atrisk- vs -risktable- option***From:*Phil Clayton <philclayton@internode.on.net>

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