[R] Logistic regression

[Dieter Menne]

Guillaume Brutel <guillaume.brutel <at> yahoo.fr> writes:

> I am trying to fit a non linear regression model to time series data.
> 
> If I do this:
> reg.logis = nls(myVar~SSlogis(myTime,Asym,xmid,scal))
> I get this error message (translated to English from French):
> Erreur in nls(y ~ 1/(1 + exp((xmid - x)/scal)), data = xy, start = 
> list(xmid = aux[1],  :
>   le pas 0.000488281 became inferior to 'minFactor' of 0.000976562

If it occurs after a few iterations (was it verbose=TRUE; sorry, no docs at
hand), almost always means that there is no unique solution. Are you sure that
your data  level out at 1? Or is a normalization factor needed? Try to repost
with the original data set if possible. This error message might also turn up
when the start values were totally off, so try to plot the curve and the data
with the start values.

Setting minFactor never helped for me in that case.

Dieter