Re: [R] nls not solving

From: Schatzi <>
Date: Tue, 01 Mar 2011 06:38:50 -0800 (PST)

Here is a reply by Bart:
Yes you're right (I should have taken off my glasses and looked closer). However, the argument is essentially the same:

Suppose you have a solution with a,b,k,l. Then for any positive c, [a+b-bc] + [bc] + (bc) *exp(kl')exp(-kx) is also a solution, where l' = l - log(c)/k .


(Feel free to post this correction if you like)

This is from me:
The problem with dropping the "l" parameter is that it is supposed to account for the lag component. This equation was published in the literature and has been being solved in SAS. When I put it in excel, it solves, but not very well as it comes to a different solution for each time that I change the starting values. As such, I'm not sure how SAS solves for it and I'm not sure what I should do about the equation. Maybe I should just drop the parameter "a." Thanks for the help.

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