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From |
keith Farnsworth <k.farnsworth@qub.ac.uk> |

To |
statalist@hsphsun2.harvard.edu |

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

Date |
Tue, 24 May 2005 13:13:20 +0100 |

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 FarnsworthI 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.* * For searches and help try: * http://www.stata.com/support/faqs/res/findit.html * http://www.stata.com/support/statalist/faq * http://www.ats.ucla.edu/stat/stata/

Dr Keith Farnsworth Lecturer in Mathematical and Behavioural Ecology Queens University Belfast Medical Biology Centre 97 Lisburn Road Belfast BT9 7BL Northern Ireland phone +44 (0)2890 272352 fax +44 (0)2890 236505 * * For searches and help try: * http://www.stata.com/support/faqs/res/findit.html * http://www.stata.com/support/statalist/faq * http://www.ats.ucla.edu/stat/stata/

**References**:**st: RE: broken stick (piecewise linear) regression***From:*"Nick Cox" <n.j.cox@durham.ac.uk>

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