# [R] Linear Model with curve fitting parameter?

Steven McKinney smckinney at bccrc.ca
Fri Apr 1 03:34:07 CEST 2011

```> -----Original Message-----
> From: r-help-bounces at r-project.org [mailto:r-help-bounces at r-project.org] On Behalf Of stephen sefick
> Sent: March-31-11 3:38 PM
> To: R help
> Subject: [R] Linear Model with curve fitting parameter?
>
> I have a model Q=K*A*(R^r)*(S^s)
>
> A, R, and S are data I have and K is a curve fitting parameter.  I
> have linearized as
>
> log(Q)=log(K)+log(A)+r*log(R)+s*log(S)
>
> I have taken the log of the data that I have and this is the model
> formula without the K part
>
> lm(Q~offset(A)+R+S, data=x)
>
> What is the formula that I should use?

Let Z = Q - A for your logged data.

Fitting lm(Z ~ R + S, data = x) should yield
intercept parameter estimate = estimate for log(K)
R coefficient parameter estimate = estimate for r
S coefficient parameter estimate = estimate for s

Steven McKinney

Statistician
Molecular Oncology and Breast Cancer Program
British Columbia Cancer Research Centre

>
> Thanks for all of your help.  I can provide a subset of data if necessary.
>
>
>
> --
> Stephen Sefick
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