Re: [R] how to fit a curve of form Y = X^Z

From: Philipp Pagel <p.pagel_at_wzw.tum.de>
Date: Tue, 17 Jun 2008 18:47:22 +0200

> I have two variables X and Y, and think that Y is related
> to X by a function of the form : Y = X^Z, where Z is < 1.
> However, I'm not sure how to find the best-fit equation to
> fit my data to a curve of this form using R. Have you any ideas?

You can use nlm() to fit a non-linear model. Another option would be to fit a linear model to log-log transformed data. However, if you are actually trying to fit to a power-law distribution you may want to have a look at these references:

Goldstein, M.; Morris, S. & Yen, G.
Problems with Fitting to the Power-Law Distribution European Physical Journal B, 2004, 41, 255-258

Newman, M. E. J.
Power laws, Pareto distributions and Zipf's law Contemporary Physics, 2005, 46, 323

cu

        Philipp

-- 
Dr. Philipp Pagel
Lehrstuhl für Genomorientierte Bioinformatik
Technische Universität München
Wissenschaftszentrum Weihenstephan
85350 Freising, Germany
http://mips.gsf.de/staff/pagel

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