Re: [R] Confidence intervals and polynomial fits

From: David Winsemius <dwinsemius_at_comcast.net>
Date: Fri, 06 May 2011 16:27:17 -0400

On May 6, 2011, at 4:16 PM, Ben Haller wrote:
>
>
> As for correlated coefficients: x, x^2, x^3 etc. would obviously be
> highly correlated, for values close to zero.

Not just for x close to zero:

 > cor( (10:20)^2, (10:20)^3 )
[1] 0.9961938
 > cor( (100:200)^2, (100:200)^3 )
[1] 0.9966219

> Is this what you mean, as a potential source of problems? Or if you
> mean that the various other terms in my model might be correlated
> with x, that is not the case; each independent variable is
> completely uncorrelated with the others (this data comes from
> simulations, so the independent variables for each data point were
> in fact chosen by random drawing).
>
> It didn't seem easy to post an example, since my dataset is so
> large, but if either of you would be willing to look at this
> further, I could upload my dataset to a web server somewhere and
> post a link to it. In any case, thanks very much for your help;
> I'll look into the things you mentioned.
>
> Ben Haller
> McGill University
>
> http://biology.mcgill.ca/grad/ben/

David Winsemius, MD
West Hartford, CT



R-help_at_r-project.org mailing list
https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide http://www.R-project.org/posting-guide.html and provide commented, minimal, self-contained, reproducible code. Received on Fri 06 May 2011 - 20:29:01 GMT

This quarter's messages: by month, or sorted: [ by date ] [ by thread ] [ by subject ] [ by author ]

All messages

Archive maintained by Robert King, hosted by the discipline of statistics at the University of Newcastle, Australia.
Archive generated by hypermail 2.2.0, at Sat 07 May 2011 - 14:50:05 GMT.

Mailing list information is available at https://stat.ethz.ch/mailman/listinfo/r-help. Please read the posting guide before posting to the list.

list of date sections of archive