[R] Beginners Question: Make nlm work
ahenningsen at email.uni-kiel.de
Thu Aug 26 10:13:06 CEST 2004
did you try "nls" (nonlinear least squares)? "?nlm" says:
"For nonlinear regression, 'nls' may be better".
Another option would be "optim".
On Thursday 26 August 2004 01:07, Johannes Graumann wrote:
> I'm new to this and am trying to teach myself some R by plotting
> biological data. The growth curve in question is supposed to be fitted
> to the Verhulst equation, which may be transcribed as follows:
> - for a known population density (0.008) at t(0).
> I am trying to rework the example from "An Introduction to R" (p. 72)
> for my case and am failing miserably. Could somebody glance over the
> code below and nudge me into the right direction - I must have some
> major conceptual problem which can't be solved by me staring at it ...
> Since I'm repeating something I have done with gnuplot I know that 3 and
> 4e-3 as starting values for the fit are appropriate ...
> Thanks for any hint,
> VH <- function(p) y ~ p/(1+((p-0.008)/0.008)*exp(-(p*x)))
> plot(x, y, xlab="Time (h)",ylab=expression(OD[~nm]),las=1)
> out <- nlm(VH, p = c(3, 4e-3), hessian = TRUE)
> R-help at stat.math.ethz.ch mailing list
> PLEASE do read the posting guide!
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ahenningsen at agric-econ.uni-kiel.de
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