[R] nls not accepting control parameter?

[Peter Ehlers]

Hello Rainer,

I think that your problem is with trying to fit a logistic model to
data that don't support that model. Removing the first two points
from your data will work (but of course it may not represent reality).
The logistic function does not exhibit the kind of minimum that
your data suggest.

  -Peter Ehlers

Rainer M Krug wrote:
> Hi
> 
> I want to change a control parameter for an nls () as I am getting an error
> message  "step factor 0.000488281 reduced below 'minFactor' of 0.000976562".
> Despite all tries, it seems that the control parameter of the nls, does not
> seem to get handed down to the function itself, or the error message is
> using a different one.
> 
> Below system info and an example highlighting the problem.
> 
> Thanks,
> 
> Rainer
> 
> 
>> version               _
> platform       i486-pc-linux-gnu
> arch           i486
> os             linux-gnu
> system         i486, linux-gnu
> status
> major          2
> minor          9.2
> year           2009
> month          08
> day            24
> svn rev        49384
> language       R
> version.string R version 2.9.2 (2009-08-24)
> 
>> sessionInfo()
> R version 2.9.2 (2009-08-24)
> i486-pc-linux-gnu
> 
> locale:
> LC_CTYPE=en_ZA.UTF-8;LC_NUMERIC=C;LC_TIME=en_ZA.UTF-8;LC_COLLATE=en_ZA.UTF-8;LC_MONETARY=C;LC_MESSAGES=en_ZA.UTF-8;LC_PAPER=en_ZA.UTF-8;LC_NAME=C;LC_ADDRESS=C;LC_TELEPHONE=C;LC_MEASUREMENT=en_ZA.UTF-8;LC_IDENTIFICATION=C
> 
> attached base packages:
> [1] stats     graphics  grDevices utils     datasets  methods   base
> 
> other attached packages:
> [1] R.utils_1.2.0     R.oo_1.5.0        R.methodsS3_1.0.3 maptools_0.7-26
> [5] sp_0.9-44         foreign_0.8-37
> 
> loaded via a namespace (and not attached):
> [1] grid_2.9.2      lattice_0.17-25
> 
> 
> #############################################
> 
> EXAMPLE:
> 
> dat <- data.frame(
>                   x = 2006:2037,
>                   y = c(143088, 140218, 137964,
>                     138313, 140005, 141483, 142365,
>                     144114, 145335, 146958, 148584,
>                     149398, 151074, 152241, 153919,
>                     155580, 157258, 158981, 160591,
>                     162126, 163743, 165213, 166695,
>                     168023, 169522, 170746, 172057,
>                     173287, 173977, 175232, 176308,
>                     177484)
>                   )
> 
> nls( y ~ SSlogis(x, Asym, xmid, scal), data = dat, trace=TRUE)
> 
> (newMinFactor <- 1/(4*1024))
> nls( y ~ SSlogis(x, Asym, xmid, scal), data = dat,
> control=nls.control(minFactor=newMinFactor), trace=TRUE)
> nls( y ~ SSlogis(x, Asym, xmid, scal), data = dat,
> control=c(minFactor=newMinFactor), trace=TRUE)
> 
> 
> (newMinFactor <- 4/1024)
> nls( y ~ SSlogis(x, Asym, xmid, scal), data = dat,
> control=nls.control(minFactor=newMinFactor), trace=TRUE)
> nls( y ~ SSlogis(x, Asym, xmid, scal), data = dat,
> control=c(minFactor=newMinFactor), trace=TRUE)
> 
> 
>