[R] Analysis and graphics by groups

[Bilonick, Richard A]

Unless I misunderstand, I think you might want the nlsList function from the nlme package. It will let you fit a nonlinear model for grouped data. You use "|" to separate the model formula from the grouping factor.

Rick
________________________________________
From: r-help-bounces at r-project.org [r-help-bounces at r-project.org] on behalf of Andrew Robinson [A.Robinson at ms.unimelb.edu.au]
Sent: Friday, April 29, 2011 8:05 PM
To: Cristiano Yuji Sasada Sato
Cc: r-help at r-project.org
Subject: Re: [R] Analysis and graphics by groups

hi Christiano,

the error is that FUN is not a function.  That is true, the argument
that you are passing to FUN is a different class. Instead of fx, for
example, where fx is your model code below, try to write it as a
function of the arguments that you want to split by Cerca.

You might try to construct a minimal, reproducible, commented example
to help us explain what you need to do.

I don't have the gapply function and I don't know which package it is
in (perhaps you could provide that  information next time) so I can't
help more than that.

Andrew

On Fri, Apr 29, 2011 at 04:31:51PM -0300, Cristiano Yuji Sasada Sato wrote:
> Hello,
>
> This is my first post in this e-mail list and I hope it's enough to justify
> calling for help. In case it's not, sorry.
>
> I'm trying to do analysis and graphics using a factor as a criteria to split
> data and do the analysis/graphics for each subset of data.
>
> Right now what I'm trying to do is to fit and plot the following logistic
> model, according to a third variable named "Cerca":
> dm_fit_T<-nls(nDMTRBgm2~(K/(1+((K-nDMTRBgm2.T.1)/nDMTRBgm2.T.1)*exp(-r))),perieph,start=list(K=3,r=0.2),trace=T)
>
> I've found a function called gapply which seems to be what I need, but it
> doesn't seem to work. This is the argument I've used:
> gapply(perieph,FUN=nls(nDMTRBgm2~(K/(1+((K-nDMTRBgm2.T.1)/nDMTRBgm2.T.1)*exp(-r))),perieph,start=list(K=3,r=0.2),trace=T),groups="Cerca")
>
> But I get this error message returned:
> > Error in get(as.character(FUN), mode = "function", envir = envir) :
> object 'FUN' of mode 'function' was not found
>
> Can you help me doing this non-linear regression by groups work?
>
> Also, after I manage making the regression, I'd also need fitting a line to
> the nDMTRBgm2~nDMTRBgm2.T.1 data using the same model above. I've used
> plotfit to do that with one nlm data set. Is it possible to fit each group
> trend line and data with different colours/symbols  in one same graphic?
>
> Thank you,
> Cristiano
>
> --
> Cristiano Yuji Sasada Sato
> Doutorando
> Programa de P?s-Gradua??o em Ecologia e Evolu??o - IBRAG / UERJ
> Laborat?rio de Ecologia de Rios e C?rregos
> Departamento de Ecologia - Universidade do Estado do Rio de Janeiro
>
>       [[alternative HTML version deleted]]
>

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--
Andrew Robinson
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