How to calculate the area of a fit curve?

Hi, I must calculate the area of 4 fit curves.

I wrote:

   myfitga1_P1P2graf= fit(eVc.',ckgran.','a1_P1graf*exp(-((x-285)/c1_P1graf)^2)+a1_P2graf*exp(-((x-287.8)/c1_P2graf)^2)','StartPoint',[start_point start_point start_point start_point]);
    myfitga1_P1P2P3graf= fit(eVc.',ckgran.','a1_P1graf*exp(-((x-285)/c1_P1graf)^2)+a1_P2graf*exp(-((x-287.8)/c1_P2graf)^2+a1_P3graf*exp(-((x-292.2)/c1_P3)^2))','StartPoint',[start_point start_point start_point start_point start_point start_point]);
   syms eVc;
   AreaP1P2graf=int(myfitga1_P1P2graf,eVc,emin,emax);
    AreaP1P2P3graf=int(myfitga1_P1P2P3graf,eVc,emin,emax);
    myfitga1_P1P2= fit(eVc.',ckxfit.','a1_P1*exp(-((x-285)/c1_P1)^2)+a1_P2*exp(-((x-287.8)/c1_P2)^2)','StartPoint',[start_point start_point start_point start_point]);
    myfitga1_P1P2P3= fit(eVc.',ckxfit.','a1_P1*exp(-((x-285)/c1_P1)^2)+a1_P2*exp(-((x-287.8)/c1_P2)^2+a1_P3*exp(-((x-292.2)/c1_P3)^2))','StartPoint',[start_point start_point start_point start_point start_point start_point]);
    AreaP1P2=int(myfitga1_P1P2,eVc,emin,emax);
    AreaP1P2P3=int(myfitga1_P1P2P3,eVc,emin,emax);

but I get this error:

Undefined function 'int' for input arguments of type 'cfit'.

How to fix it? Best regards

Answer 1

[Ameer Hamza]

You are getting the error because int object only accept symbolic expressions where fit() function returns a cfit object. To integrate the cfit object, thre is no need to use syms, use curve fittinng toolbox function integrate as follow

AreaP1P2graf = integrate(myfitga1_P1P2graf ,emin, emax);

[Fc Fc]

Thank you! it worked!

[Ameer Hamza]

You are welcome.