Hello everyone,
 
I'm trying to test the accurracy of R on the Eckerle4 dataset from NIST and
I don't understand how the control option of the nls function works. 
I tought nls(...) was equivalent to nls(...control=nls.control()) i.e nls.control() was the default value of control, but here is the error I get :
 
> n2=nls(V1~(b1/b2) * exp(-0.5*((V2-b3)/b2)^2),data=ecker,start=list(b1=1.5,b2=5,b3=450,control=nls.control()))
Error in nlsModel(formula, mf, start) : singular gradient matrix at initial parameter estimates

while I get  no error without setting the control option with the same other parameters.
 
I see that R didn't manage to solve the Eckerle4 regression problem from start one while Splus can do it with the nlregb option.
Is there something equivalent for R now?
 
Otherwise, I found that R 2.0.1 was performing better than SAS 9.1 on the NIST Datasets in general.
 
Best regards,
 
Anthony Landrevie
 
 

		
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