nls() and "singular grandient"

Many people could help you, but the question is too general.  In 
brief, it means that the algorithm has found a place where the 
(estimated?) matrix of first or second partial derivatives is of reduced 
rank, and it refuses to do more.  For such problems, I often use "optim". 

      If you need more specifics, PLEASE do read the posting guide! 
"http://www.R-project.org/posting-guide.html", prepare a very simple 
example of what you get, and submit that to this list.  Many people find 
answers to their questions in the process of preparing a post following 
this guide, and those that don't, I believe, are more likely to get more 
informative replies. 

      spencer graves

Hello,

I have a problem with nls() when I want to fit a model with more than two
parameters to be fitted which are written as start=list(a1=,a2=,a3=,...).
Everytime, it displays:'error... singular gradient'
it's a real pain!!! 

Hope sb knows something about this

Thanks

GS

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