Re: st: RE: broken stick (piecewise linear) regression

[keith Farnsworth <k.farnsworth@qub.ac.uk>]

Thanks, Nick, but I looked at mkspline before and realised that it 
specifically requires the knot point, whereas the problem I have, 
addressed by Bacon and Watts, is to find the best fit knot point i.e - 
estimating the transition between two intersecting straight lines. 
Unless there is something you can do with mkspline that is not in the 
documentation, I don't see that it can fit the knot.

Any other idea?


Keith.

On Tuesday, May 24, 2005, at 12:55 Europe/Dublin, Nick Cox wrote:


> . search mkspline
>
> should help. See both entries.
>
> Nick
> n.j.cox@durham.ac.uk
>
> keith Farnsworth
>
> > I intend to fit a broken stick model following Bacon and Watts
> > "Estimating the transition between two intersecting straight lines",
> > Biometrika 1971. I have seen code for this to use the S or R
> > package's
> > nls, which I suspect uses maximum likelihood (but not sure) [see
> > http://www.biostat.wustl.edu/archives/html/s-news/2000-04/
> > msg00215.html].
> >
> > I am not an S user, I am a Stata enthusiast!
> > However, I found no reference to this kind of model in Stata
> > searches.
> > I hope someone with more experience than me can explain how
> > Stata will
> > implement the Bacon and Watts model.
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Dr Keith Farnsworth
Lecturer in Mathematical and Behavioural Ecology
Queens University Belfast

Medical Biology Centre
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