how to find the horizontal Asymptotes of fitted curve equation for a data set

I have a data for (y,vor). I have used cftool to get fitted function for the input data. I want to know how to get the the horizontal asymptote of the fitted function as it approches zero (vor=0).

I have tried to use limit function but it does not work. I saved the fitted function as fittedmodel, then i used limit function to get teh asymtote

limit(fittedmodel,x,0)
Check for missing argument or incorrect argument data type in call to function 'limit'.

Answer 1

[Soumya]

Hi @zein,

The ‘limit’ function in MATLAB which is a part of the Symbolic Math Toolbox, is designed to operate on symbolic variables and symbolic expressions. When the function ‘cftool’ from the Curve Fitting Toolbox creates a fitted model, it returns a ‘cfit’ object. A ‘cfit’ object is an object that encapsulates the fitted function, but it is not a symbolic expression, hence does not work with ‘cftool’ function.

To enable symbolic analysis, the object created by the ‘cfit’ function must first be converted into a symbolic expression using the ‘formula’ function:

fexpr = formula(fittedmodel); 

Once in symbolic form, MATLAB’s Symbolic Math Toolbox can be used to compute the limit of the function as the independent variable approaches a specified value.

For detailed information on these functions, please refer to the following documentation:

• https://www.mathworks.com/help/curvefit/cfit.formula.html
• https://www.mathworks.com/help/curvefit/curve-and-surface-fitting-objects-and-object-functions.html

I hope this helps!