Re: [Gnuplot-info] Gnuplot - Problem with exponential fit

[Junghun S. <jh...@ef...>]

Such things happen when the orders of fitting parameters are too
different. I meant, if lambda is 0.7, then n_0 should also be around 1
or 10. So try with a function like:

f(x) = 1e12*n_0*exp((-x)/lambda)

and initial n_0 at 3.

On Mon, Jul 19, 2010 at 6:18 PM, f.hasenbeck <f.h...@fz...> wrote:
>  Hi!
>
> I have a problem with an exponential fit. My script looks like this:
>
>
> n_0 = 3.0e+12
> lambda = 0.7
> f(x) = n_0*exp((-x)/lambda)
>
> fit f(x) '../95896_029/c_001/run/rad_profile_exp_decay_torzone_1.txt' u
> ($4-217):2 via n_0, lambda
>
>
> I am using the two fitting parameters n_0 and lambda, but only lambda is
> varied by GNUPLOT, no matter which starting value I use vor n_0. This
> seems strange since a variation of n_0 also should be able to provide
> better fitting results. Is there a solution to this problem so that
> GNUPLOT also varies n_0?
>
> Thank you very much for your help!
>
> Felix Hasenbeck
>
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