[R] breakpoints and nonlinear regression

[Achim Zeileis]

On Tue, 17 Jan 2012, crimsonengineer87 wrote:

> Thanks for the comments everyone. I was hoping to not have to find someone in
> the stats department ... well, we'll see.
>
> So in response to Z's comment ... I have tried breakpoints(Na ~ yield) 
> and I did expect to get something continuous.

You won't. The result may be close to continuous (depending on your data) 
but there is no inherent continuity restriction.

That's what "segmented" does (that Rolf already pointed to). See

Vito M. R. Muggeo (2008). segmented: an R Package to Fit Regression Models 
with Broken-Line Relationships. R News, 8/1, 20-25. URL 
http://CRAN.R-project.org/doc/Rnews/.

> The idea was to get two or three
> linear functions making up the curve. And then from there, get a CI from
> these lines. Of course, it wouldn't be good. (This is coming from a
> non-stats guy ... I'm a civil engineer by degree and am now learning to be a
> modeler as a grad student!). Do you know of any more examples of
> breakpoints? The examples in the references are great, but I can't seem to
> get it right.
>
> Thanks again.
>
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