Re: [R] Error 'singular gradient' in nonlinear model fitting

From: Ravi Varadhan <rvaradhan_at_jhmi.edu>
Date: Fri, 15 Feb 2008 12:48:19 -0500

Try a different set of starting values for alpha & beta.

Ravi.



Ravi Varadhan, Ph.D.

Assistant Professor, The Center on Aging and Health

Division of Geriatric Medicine and Gerontology

Johns Hopkins University

Ph: (410) 502-2619

Fax: (410) 614-9625

Email: rvaradhan_at_jhmi.edu

Webpage: http://www.jhsph.edu/agingandhealth/People/Faculty/Varadhan.html  



-----Original Message-----
From: r-help-bounces_at_r-project.org [mailto:r-help-bounces_at_r-project.org] On Behalf Of HongSheng Liao
Sent: Friday, February 15, 2008 12:42 PM To: r-help_at_r-project.org
Subject: [R] Error 'singular gradient' in nonlinear model fitting

w.age.female.2004 <- nls(WEIGHT ~ (alpha*TOTAL^beta)/454,

                        start=list(alpha=1, beta=3),
                        data=spottedseatrout2004.female.data)

I am trying to fit above model to length-weight data of a fish species (spotted seatrout) by year (1999-2006). The convergence occurred for all the years except 2002 and 2004. In these two year, R shows the error called 'singular gradient' in the model. Could anyone please help me to fix the error? I don't think there are any problems with my data because I can fit the same model to 2004 data without any problems using SAS. Thank you very much in advance.

Hongsheng (Hank) Liao, Ph.D.
Lab Manager
Center for Quantitative Fisheries Ecology 800 West 46th Street
Old Dominion University
Norfolk, Virginia 23508
Phone:757.683.4571

Fax:757.683.5293



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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 15 Feb 2008 - 17:51:20 GMT

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