how to extract the formula from fit function?

75 vues (au cours des 30 derniers jours)
Amin  Tehrani
Amin Tehrani le 29 Nov 2017
Commenté : Walter Roberson le 16 Avr 2024 à 20:48
I want to use fit function to get the formula with its coefficient for my data. so i have used: [curve, goodness, output] = fit(fk,Rfft,'linearinterp'); in case of 'poly1' or 'poly2' the curve variable (which is in cfit format) shows the formula with its coefficients however when i use linearinterp the curve does not show the formula, it just says "piecewise polynomial". i need to get the formula with its coefficients. does anyone have any idea how to get the formula?
<<
>>

Réponse acceptée

Vishwas
Vishwas le 7 Déc 2017
There really isn't a formula for the surface. It's a piecewise linear surface so it's a single formula for a plane at each location of your data making it many formulas altogether.

Plus de réponses (1)

Bowen Song
Bowen Song le 16 Mar 2019
Modifié(e) : Bowen Song le 16 Mar 2019
Treat it as a string... lol check this out
[fitresult{1}, gof(1)] = fit( [xData, yData], zData, ft );
... from above you get your sfit or what not
f = string(formula(fitresult{1})); // get the formular in string format
names = coeffnames(fitresult{1}); // get the coeff names
vals = coeffvalues(fitresult{1}); // get those values
for i = 1:length(names)
f = strrep(f,string(names(i)),string(vals(i))); // replace the coeff names with values
end
eval(f) // muhaha
  3 commentaires
Xiyan Li
Xiyan Li le 16 Avr 2024 à 16:24
I wonder how to get the equation out after piecewise fitting? It makes no sense to me without gettting the equation out.
Walter Roberson
Walter Roberson le 16 Avr 2024 à 20:48
The output is a piecewise polynomial. It does not have a single equation. It is effectively a list of equations that are each valid over a specific range.

Connectez-vous pour commenter.

Catégories

En savoir plus sur Fit Postprocessing dans Help Center et File Exchange

Community Treasure Hunt

Find the treasures in MATLAB Central and discover how the community can help you!

Start Hunting!

Translated by