On Mon, Oct 18, 2004 at 08:48:40AM -0700, Thomas Lumley wrote:
> On Sun, 17 Oct 2004, Kuan-Ta Chen wrote:
>
> >Hi, all:
> >
> >I find survreg {survival} has provided many distributions such as weibull,
> >lognormal, etc. But I wonder why it doesn't have the support for gamma
> >distribution since it should be a good distr. in lifetime analysis. Can
> >anybody figure out the reason?
>
> Presumably the actual reason is because Terry Therneau didn't need to use
> the Gamma model. However, all the distributions in survreg are
> location-scale families,
But only after a time transformation (usually the log transformation) in
most cases (exponential, Weibull, lognormal, ...)
> which the Gamma is not, so the basic algorithm
> would have to be different.
which also holds for the Gamma; log(Gamma) is a location-scale family. So
the basic algorithm should work after all? (Haven't tried it myself,
though.)
Göran
--
Göran Broström tel: +46 90 786 5223
Department of Statistics fax: +46 90 786 6614
Umeå University http://www.stat.umu.se/egna/gb/
SE-90187 Umeå, Sweden e-mail: [EMAIL PROTECTED]
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