[R] retrieving coefficients from nls() when it fails to converge

[Potter, David M]

Hi --

I am fitting four-parameter logistic regression models using nls(),
typically within the body of a loop.  Sometimes a fit fails to converge and
yet I would like to pull off the coefficients from the last iteration and
use them to compute backfitted (i.e., inverse prediction) values.

Note: To ignore the fit completely, but have the loop continue, I have
successfully used try(), but in this case the fits are sufficient for
getting backfitted values (even though the coefficients are poorly
estimated), so I need the actual coefficients.

R information:

platform i386-pc-mingw32
arch     i386           
os       mingw32        
system   i386, mingw32  
status                  
major    1              
minor    7.1            
year     2003           
month    06             
day      16             
language R  

Thanks for your help.

David

__
David M. Potter
Groton Nonclinical Statistics
Pfizer Global Research and Development



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