Message-ID: <Pine.A41.4.44.0203041518200.144620-100000@homer10.u.washington.edu>
Date: 2002-03-04T23:19:08Z
From: Thomas Lumley
Subject: Solving quadratic functions
In-Reply-To: <1F8EDF0AE0FFC643BC8FE577BC4919E624AD99@tomtom-wb.mel.foodscience.afisc.csiro.au>
On Tue, 5 Mar 2002 Peter.Watkins at foodscience.afisc.csiro.au wrote:
> I'm examining the use of the 'lm' function to solve quadratic functions.
>
> With S+ 2000, the 'lm' function can be used to solve eqns such as x1 + x2 +
> x1^2 + x2^2 + x1*x2.
> But, when trying this same eqn with R, the software does not produce any
> coefficients for x1^2 or x2^2.
>
> Is this a common problem?
Well, it's a FAQ
Differences between R & S: Models
Whereas in S, you would use lm(y ~ x^3) to regress y on x^3, in R, you
have to insulate powers of numeric vectors (using I()), i.e., you have
to use lm(y ~ I(x^3)).
-thomas
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