From P.Dalgaard at biostat.ku.dk  Fri Jan  4 18:23:33 2008
From: P.Dalgaard at biostat.ku.dk (Peter Dalgaard)
Date: Fri, 04 Jan 2008 18:23:33 +0100
Subject: [Rd] nls (with SSlogis model and upper limit) never
	returns	(PR#10544)
In-Reply-To: <20080104144526.F378D2834618@mail.pubhealth.ku.dk>
References: <20080104144526.F378D2834618@mail.pubhealth.ku.dk>
Message-ID: <477E6B95.50906@biostat.ku.dk>

hendrik.weisser at gmx.net wrote:
> Full_Name: Hendrik Weisser
> Version: 2.6.1
> OS: Linux
> Submission from: (NULL) (139.19.102.218)
>
>
> The following computation never finishes and locks R up:
>
>   
>> values <- list(x=10:30, y=c(23.85, 28.805, 28.195, 26.23, 25.005, 20.475,
>>     
> 17.33, 14.97, 11.765, 8.857, 5.3725, 5.16, 4.2105, 2.929, 2.174, 1.25, 1.0255,
> 0.612, 0.556, 0.4025, 0.173))
>   
>> y.max <- max(values$y)
>> model <- nls(y ~ SSlogis(x, asym, xmid, scal), data=values, algorithm="port",
>>     
> start=c(asym=y.max, xmid=15, scal=-0.5), upper=c(y.max, Inf, Inf))
>
> This used to work with R version 2.5.1 patched.
> The problem does _not_ occur if the parameter "scal=-0.5" in the nls call is
> changed, e. g. to "scal=-0.6" or "scal=-0.4".
> Simply calling "model <- nls(y ~ SSlogis(x, asym, xmid, scal), data=values)"
> also works, but this does not use the upper bound for the asym parameter, which
> was the point.
>
>   
"Linux" is not a good enough description of your platform.

This works fine on SUSE 10.2/x86_64.


-- 
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  c/ /'_ --- Dept. of Biostatistics     PO Box 2099, 1014 Cph. K
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[Rd] nls (with SSlogis model and upper limit) never returns (PR#10544)
Peter Dalgaard