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Re: st: problem obtaining hazard estimates
Apologies, this is a repost with a proper subject.
Steinar Fossedal <Steinar.Fossedal@nhh.no> is getting a error while using
-sts graph, hazard-.
Steichen, Thomas J. <SteichT@rjrt.com> checked Steiner's example but did not
get an error.
> I am experiencing problems obtaining a Kaplan-Meier estimate of the
> hazard function. Using -sts graph, haz- returns an error "Variable __ub
> not found" r(111). The error does not, however, appear when requesting
> the surivival function of the same data. I can reproduce the error using
> the leukemia data from stata-press (see printout below), even after a
> complete reinstall of Stata 9. How complete it actually was is hard to
> tell, my settings were still identical to what they were prior to the
> reinstall even though I renamed the old "C:\Program Files\Stata9-folder"
> to Stata9_old. Where else does Stata store information?
The example was:
> . use http://www.stata-press.com/data/r8/leukemia, clear
> (output omitted)
> . stset weeks, failure(relapse)
> (output omitted)
> . sts graph, haz
> failure _d: relapse
> analysis time _t: weeks
> variable __ub not found
Steiner found a problem in the ado-file for -sts graph, hazard-. The above
error is caused by turning off variable abbreviations in Stata (see -help
set_varabbrev-). The reference to '__ub' is in fact an abbreviation of
A fix to -sts graph- will be available in a future ado-file update.
In the mean time, Steiner can turn variable abbreviations back on to get
around this problem.
> Until now I have been using -sts gen haz=h- instead, but today, by a one
> time fluke, stata suddenly returned different results compared to
> earlier. I would normally be willing to write this off as some fault on
> my part had it not been for the disturbing fact that the fluke-results
> were a lot more in sync with the predictions from my models. The results
> are, however, not reproducable in the same session even after doing no
> changes to the dataset.
> I am now wondering if the two problems are somehow related, and fear
> there is something wrong with the hazard-estimates I have been
> recieving. Can someone confirm the problem, or suggest a way to handle
We are confident that -sts generate- is computing the hazard-estimates
correctly. The variable abbreviations setting does not affect the results
from -sts generate-.
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