[R] Obtaining a quadratic function igven three points on a curve

[Joshua Wiley]

Many thanks for the correction David.

Josh

On Thu, Jan 20, 2011 at 7:17 AM, David Scott <d.scott at auckland.ac.nz> wrote:
> I think you need poly(X, 2,  raw = TRUE) to interpret the coefficients in
> the manner described below.
>
> poly uses orthogonal polynomials by default:
>
> poly                   package:stats                   R Documentation
>
> Compute Orthogonal Polynomials
>
> Description:
>
>     Returns or evaluates orthogonal polynomials of degree 1 to
>     'degree' over the specified set of points 'x'. These are all
>     orthogonal to the constant polynomial of degree 0.  Alternatively,
>     evaluate raw polynomials.
>
> David Scott
>
[snip]
> --
> _________________________________________________________________
> David Scott     Department of Statistics
>                The University of Auckland, PB 92019
>                Auckland 1142,    NEW ZEALAND
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> Email:  d.scott at auckland.ac.nz,  Fax: +64 9 373 7018
>
> Director of Consulting, Department of Statistics