# Function with multiple input parameters to be determined through fitting

3 views (last 30 days)

Show older comments

Hi, I have a function to be fitted to some experimental data, but this function has multiple fitting parameters (6 parameters). I know that one of the ways to find these fitting parameters is to pass the function, the inital guess to the parameters and the lower and upper bounds into the lsqcurvefit function.

I have already created the function, but it seems like the software doesn't know that the p(1),p(2), p(3)... are parameters. Sorry if the function is very long.

What I wanted was p to be a vector with 6 elements p(1) p(2) p(3) p(4) p(5) p(6) but it seems like the software cant differentiate betwen p and p(1) p(2) p(3) p(4) p(5) p(6). When I try running the code, the error message I got was "Not enough input arguments"

Thank you for helping

function F = EM_SS(p, E_p)

F = p(1)*(2*pi*sqrt(p(4))/E_p)*(1/p(6))*(int(sech(((E_p - E)./p(6)))*(1 + 10*p(5)*(E - p(3)) + 126*p(5)^2*(E - p(3))^2)/(1 - exp(-2*pi*sqrt(p(4)/(E - p(3))))), E, p(3), Inf, 'ArrayValued', 1)) + p(2)*(2*pi*p(4)^3/2)*1/p(6)*((1/1^3)*sech((E_p - p(3) + p(4)/1^2)./p(6)) + (1/2^3)*sech((E_p - p(3) + p(4)/2^2)./p(6)) + (1/3^3)*sech((E_p - p(3) + p(4)/3^2)./p(6)) + (1/4^3)*sech((E_p - p(3) + p(4)/4^2)./p(6)) + (1/5^3)*sech((E_p - p(3) + p(4)/5^2)./p(6)) + (1/6^3)*sech((E_p - p(3) + p(4)/6^2)./p(6)) + (1/7^3)*sech((E_p - p(3) + p(4)/7^2)./p(6)));

end

### Accepted Answer

Torsten
on 7 Jun 2024

Edited: Torsten
on 8 Jun 2024

You have to use "integral" instead of "int" and loop over the elements in E_p:

EM_SS([1 1 1 1 1 1],1)

function F = EM_SS(p, e_p)

for i = 1:numel(e_p)

E_p = e_p(i);

F(i) = p(1)*(2*pi*sqrt(p(4))/E_p)*(1/p(6))*...

(integral(@(E)sech(((E_p - E)./p(6)))*(1 + 10*p(5)*(E - p(3)) + ...

126*p(5)^2*(E - p(3))^2)/(1 - exp(-2*pi*sqrt(p(4)/(E - p(3))))), p(3), Inf, 'ArrayValued', 1)) + ...

p(2)*(2*pi*p(4)^3/2)*1/p(6)*(...

(1/1^3)*sech((E_p - p(3) + p(4)/1^2)./p(6)) + ...

(1/2^3)*sech((E_p - p(3) + p(4)/2^2)./p(6)) + ...

(1/3^3)*sech((E_p - p(3) + p(4)/3^2)./p(6)) + ...

(1/4^3)*sech((E_p - p(3) + p(4)/4^2)./p(6)) + ...

(1/5^3)*sech((E_p - p(3) + p(4)/5^2)./p(6)) + ...

(1/6^3)*sech((E_p - p(3) + p(4)/6^2)./p(6)) + ...

(1/7^3)*sech((E_p - p(3) + p(4)/7^2)./p(6)));

end

end

##### 15 Comments

Torsten
on 8 Jun 2024

### More Answers (0)

### See Also

### Community Treasure Hunt

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

Start Hunting!