On Mon, Jul 9, 2012 at 3:59 PM, Terry Therneau <therneau@mayo.edu> wrote:

> Without more information, we can only guess what you did, or what you are
> seeing on the page that is "different".
>
> I'll make a random guess though.  There are about 5 ways to paramaterize
> the Weibull distribution.  The standard packages that I know, however, tend
> to use the one found in the Kalbfleisch and Prentice book The Statistical
> Analysis of Failure time Data.  This includes the survreg funciton in R and
> lifereg in SAS, and likely stata tthought I don't know that package.  The
> aftreg function in the eha package uses something different.
>

The main difference is that aftreg estimates AFT factors, i.e., the
(exponential) score of an individual accelerates time with that factor. In
survreg, expected life is multiplied by the corresponding factor (the
inverse of the previous).

>
> About 1/2 the weibull questions I see are due to a change in parameters.
>
> For this reason I have introduced an additional parameter to aftreg,
'param', in the latest version of eha. The default value is 'default'
(everything is as before) and an alternative is 'survreg' (everything is as
in survreg).

Göran

> Terry T.
>
> ---- begin included message -----
>
>
>
>
> Dear Community,
>
> I have been using two types of survival programs to analyse a data set.
>
> The first one is an R function called aftreg. The second one an STATA
> function called streg.
>
> Both of them include the same analyisis with a weibull distribution. Yet,
> results are very different.
>
> Shouldn't the results be the same?
>
> Kind regards,
> J
>
> ______________________________**________________
> R-help@r-project.org mailing list
> https://stat.ethz.ch/mailman/**listinfo/r-help<https://stat.ethz.ch/mailman/listinfo/r-help>
> PLEASE do read the posting guide http://www.R-project.org/**
> posting-guide.html <http://www.R-project.org/posting-guide.html>
> and provide commented, minimal, self-contained, reproducible code.
>



-- 
Göran Broström

	[[alternative HTML version deleted]]

