[Rd] nls (with SSlogis model and upper limit) never returns (PR#10544)

[maechler at stat.math.ethz.ch]

>>>>> "PD" == Peter Dalgaard <P.Dalgaard at biostat.ku.dk>
>>>>>     on Fri, 04 Jan 2008 18:23:33 +0100 writes:

    PD> 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.


    PD> "Linux" is not a good enough description of your platform.

    PD> This works fine on SUSE 10.2/x86_64.

It also works fine for me on

- Ubuntu 7.10("gutsy") i686
- Redhat EL 5  	       x86_64

Martin

    PD> -- 
    PD> O__  ---- Peter Dalgaard             Øster Farimagsgade 5, Entr.B
    PD> c/ /'_ --- Dept. of Biostatistics     PO Box 2099, 1014 Cph. K
    PD> (*) \(*) -- University of Copenhagen   Denmark          Ph:  (+45) 35327918
    PD> ~~~~~~~~~~ - (p.dalgaard at biostat.ku.dk)                  FAX: (+45) 35327907