This is definitely nonlinear. nls() is what you need.
On Sat, 2 Nov 2002, Timur Elzhov wrote:
> Dear R experts!
>
> I have the y(x) data (length(y) == length(x) == 10,000)
> and I want to fit it with function
>
> exp(-a1 * x) + exp(-a2 * x)
>
> a1, a2 -- are parameters to be estimated.
>
> What the "right" way to do it?
> Can I transform data to something so that linear model could be used?
> Or, I must use a non-linear model, definitely?
>
> Thank you very much.
>
>
> --
> WBR,
> Timur.
>
>
>
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