# logistic growth model

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## logistic growth model

 I want to Fit a logistic growth model for y = k *eb0+b1(age)/1 + eb0+b1(age), can some one help on how to get the initial coefficients b0 and b1? I need to estimate in order to do the regression analysis. When I run using b0=0.5 and b1=3.4818, I get the following error 397443.8 :  0.5 3.4818 Error in nls(Height ~ k * exp(b1 + b2 * Age)/(1 + exp(b1 + b2 * Age)),  :    singular gradient "please tell me what is wrong with my initials values, and how to get the initial values" ______________________________________________ [hidden email] mailing list https://stat.ethz.ch/mailman/listinfo/r-helpPLEASE do read the posting guide http://www.R-project.org/posting-guide.htmland provide commented, minimal, self-contained, reproducible code.
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## Re: logistic growth model

 Write the growth formula in an R script. Define initial par values. Input the size and age data. Plot the size and age data as points. Plot the growth model with the initial par values as a line. Play with the initial par values until you see a good agreement between the model (the line) and the data (the points). Optimise. Re-plot. Plot a residual histogram. Plot a residual scatterplot. Plot a Q-Q residual plot. HTH Rubén ____________________________________________________________________________________ Dr. Rubén Roa-Ureta AZTI - Tecnalia / Marine Research Unit Txatxarramendi Ugartea z/g 48395 Sukarrieta (Bizkaia) SPAIN > -----Mensaje original----- > De: [hidden email] > [mailto:[hidden email]] En nombre de Renalda > Enviado el: sábado, 04 de junio de 2011 6:17 > Para: [hidden email] > Asunto: [R] logistic growth model > > I want to Fit a logistic growth model for y = k > *eb0+b1(age)/1 + eb0+b1(age), can some one help on how to get > the initial coefficients b0 and b1? I need to estimate in > order to do the regression analysis. When I run using b0=0.5 > and b1=3.4818, I get the following error > > 397443.8 :  0.5 3.4818 > Error in nls(Height ~ k * exp(b1 + b2 * Age)/(1 + exp(b1 + b2 > * Age)),  : >    singular gradient > "please tell me what is wrong with my initials values, and > how to get the initial values" > > ______________________________________________ > [hidden email] 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. > ______________________________________________ [hidden email] mailing list https://stat.ethz.ch/mailman/listinfo/r-helpPLEASE do read the posting guide http://www.R-project.org/posting-guide.htmland provide commented, minimal, self-contained, reproducible code.