R help - Jul 2005 - Weighted nls

Dear R Community,
 
I am attempting to perform a weighted non-linear least squares fit.  It has
already been noted that the weights option is not yet implemented for the nls
function, but no one seems to offer any suggestions for getting around this
problem.  I am still curious if a) anyone has code they have written which
includes a weight options for nls, or b) if there is another model which would
allow least squares fitting to a non-linear function.
 
Thank you for reading this,
 
Dan

Please do your homework, as the posting guide asks you to.  

1.  From the Example section of ?nls:

## weighted nonlinear regression
Treated <- Puromycin[Puromycin$state == "treated", ]
weighted.MM <- function(resp, conc, Vm, K)
{
    ## Purpose: exactly as white book p.451 -- RHS for nls()
    ##  Weighted version of Michaelis-Menten model
    ## ------------------------------------------------------------
    ## Arguments: 'y', 'x' and the two parameters (see book)
    ## ------------------------------------------------------------
    ## Author: Martin Maechler, Date: 23 Mar 2001, 18:48

    pred <- (Vm * conc)/(K + conc)
    (resp - pred) / sqrt(pred)
}

Pur.wt <- nls( ~ weighted.MM(rate, conc, Vm, K), data = Treated,
              start = list(Vm = 200, K = 0.1),
              trace = TRUE)

2.  This has been covered several times on this list.  Search the archive.

Andy
> From: Rundle, Daniel
> 
> Dear R Community,
>  
> I am attempting to perform a weighted non-linear least 
> squares fit.  It has already been noted that the weights 
> option is not yet implemented for the nls function, but no 
> one seems to offer any suggestions for getting around this 
> problem.  I am still curious if a) anyone has code they have 
> written which includes a weight options for nls, or b) if 
> there is another model which would allow least squares 
> fitting to a non-linear function.
>  
> Thank you for reading this,
>  
> Dan
> 
> ______________________________________________
> R-help at stat.math.ethz.ch mailing list
> https://stat.ethz.ch/mailman/listinfo/r-help
> PLEASE do read the posting guide! 
> http://www.R-project.org/posting-guide.html
> 
> 
>

"Rundle, Daniel" <stdmr03 at moravian.edu> writes:
> Dear R Community,
>  
> I am attempting to perform a weighted non-linear least squares fit.
> It has already been noted that the weights option is not yet
> implemented for the nls function, but no one seems to offer any
> suggestions for getting around this problem. I am still curious if
> a) anyone has code they have written which includes a weight options
> for nls, or b) if there is another model which would allow least
> squares fitting to a non-linear function.
>  
gnls in the nlme package. Or follow the example on help(nls) immediately
after the      

## weighted nonlinear regression

(!)

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