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From |
Phil Clayton <philclayton@internode.on.net> |

To |
statalist@hsphsun2.harvard.edu |

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

Date |
Fri, 15 Apr 2011 19:45:10 +1000 |

Alex, I've just tried this with my own data and I agree with you - the -atrisk- option doesn't appear to take into account the multiple-record structure of your data. As you can see from your example, -risktable- is getting it right. I would suggest bringing this up with StataCorp. Phil On 12/04/2011, at 10:49 PM, Alex Gamma wrote: > 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 > e-mail: alex.gamma@uzh.ch > * > * 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: sts graph: different results with -atrisk- vs -risktable- option***From:*"Alex Gamma" <alex.gamma@uzh.ch>

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