gnuplot-info

[Gnuplot-info] fitting in gnuplot

[Morten H. <mor...@sm...>]

Is there a way to set up restrictions for the variables used when fitting a 
function to a data set?

---Example---

f(x)=a*x+b
fit f(x) 'example.txt' u 2:1 via a,b

but variable b must be between 1 and 10 for example

Setting a range (x or y) to fit a part of the graph is no problem. Setting 
limits/range for the individual fitting variables is my problem.

Please, Anyone!!!

morten

Re: [Gnuplot-info] fitting in gnuplot

[<HBB...@t-...>]

Morten Huse wrote:

> Is there a way to set up restrictions for the variables used when fitting a 
> function to a data set?

You have to transform a full-range fit parameter into a number that 
obeys the range requirement, e.g.

> f(x)=a*x+b
> fit f(x) 'example.txt' u 2:1 via a,b
> 
> but variable b must be between 1 and 10 for example

could be rewritten as

    limit(x,lower,upper)=lower+(upper-lower)/pi*atan(x)
    f(x)= a*x+limit(b,1,10)