Re: range of fitted variable

Tricks are given in the below

http://gnuplot-tricks.blogspot.com/2009/12/restricting-fit-parameters.html



Tatsuro


----- Original Message -----
> From: Tatsuro MATSUOKA
> To: Patrick Dupre 
> Cc: gnuplot-info> Date: 2019/6/30, S
un 08:17
> Subject: Re: [Gnuplot-info] range of fitted variable
> 
>>  Even with Marquardt-Levenberg method, you can constrain parameters.
> 
> OK. This is just my ignorance.
> Anyway, gnuplot fit uses unconstrained least square method.
> 
>>  Anyway, you can always does it in the function, and put the constrains here
>>  since conditional statement are accepted. 
> 
> help fit says
> gnuplot> help fit
>  The `fit` command fits a user-supplied real-valued expression to a set of
>  data points, using the nonlinear least-squares Marquardt-Levenberg
>  algorithm. There can be up to 12 independent variables, there is always 1
>  dependent variable, and any number of parameters can be fitted.
>  Optionally, error estimates can be input for weighting the data points.
> 
>  The basic use of `fit` is best explained by a simple example:
> 
>        f(x) = a + b*x + c*x**2
>        fit f(x) 'measured.dat' using 1:2 via a,b,c
>        plot 'measured.dat' u 1:2, f(x)
> 
>  Syntax:
>        fit {<ranges>} <expression>
>            '<datafile>' {datafile-modifiers}
>            {{unitweights} | {y|xy|z}error | errors 
> <var1>{,<var2>,...}}
>            via '<parameter file>' | 
> <var1>{,<var2>,...}
> 
> 
> ----- Original Message -----
> 
>>  From: Patrick Dupre 
>>  To: Tatsuro MATSUOKA 
>>  Cc: gnuplot 
>>  Date: 2019/6/30, Sun 07:18
>>  Subject: Re: [Gnuplot-info] range of fitted variable
>> 
>>  Hello,
>> 
>>  I am not sure that it is a helfull response.
>>  Even with Marquardt-Levenberg method, you can constrain parameters.
>>  Anyway, you can always does it in the function, and put the constrains here
>>  since conditional statement are accepted.
>> 
>>  Regards.
>> 
>>>   Subject: Re: [Gnuplot-info] range of fitted variable
>>> 
>>>   --- pdupre
>>>   > Hello,
>>>   >
>>>   > Can I set a range to the fitted variable ?
>>>   > An option could be to set a if (condition) in the fitting 
> function. Is 
>>  it possible?
>>>   >
>>>   > Thanks
>>>   >
>>> 
>>>   fit of gnuplot use Marquardt-Levenberg method.
>>>   Marquardt-Levenberg method is a uncostrained method. You cannot set 
> bounds 
>>  of parameters.
>>> 
>>>   Tatsuro
>>> 
>>> 
>> 
> 



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