How to Call a function inside for loop?

I am writing a function like this

function Eqn = eff(neff,hf)
nf=vpa(2.1511);
ns=vpa(1.5264);
nc=vpa(1.3354);
rho=1;
lambda=532.3;
Eqn = (((2*pi./lambda)*(sqrt(nf^2-neff.^2)*hf))-atan((nf/nc)^(2*rho)*sqrt ((neff.^2-nc^2)/(nf^2-neff.^2)))-atan((nf/ns)^(2*rho)*sqrt ((neff^2-ns^2)/(nf^2-neff.^2))) -(m*pi))==0;% equation 8 from paper
end

then I am calling it inside a for loop using the following code

hf = 75:20:350;
m= 0;
NEFF = zeros(size(hf)); 
for ii=1:numel(hf)
options = optimoptions('fsolve','Display','none','PlotFcn',@optimplotfirstorderopt);
neff = [0,5];
NEFF(ii)=fsolve(@(neff,hf(ii))eff(neff),neff,options
end
plot(hf, NEFF)

But I am getting an error

Invalid expression. When calling a function or indexing a variable, use parentheses. Otherwise, check for
mismatched delimiters.

what mistake I am making here? Kindly help

[Stephen23]

Your code is missing severay parentheses and that anonymous function is not defined correctly.

Replace this

NEFF(ii)=fsolve(@(neff,hf(ii))eff(neff),neff,options

with something like

fnh  = @(n)eff(n,hf(ii));
NEFF(ii) = fsolve(fnh,neff,options);

But I cannot run your code as the objective function needs to be debugged first.

Answer 1

[Sulaymon Eshkabilov]

Here is the corrected code, but still you should check the equation. The found roots are complex valued:

hf = 75:20:350;
NEFF = zeros(size(hf)); 
for ii=1:numel(hf)
options = optimoptions('fsolve','Display','none','PlotFcn',@optimplotfirstorderopt);
neff = [0; 5];
NEFF(ii)=fsolve(@(hf) eff(hf(ii), neff), neff,options);
end
%plot(hf, NEFF)

function F = eff(hf, neff)
nf=(2.1511);
ns=(1.5264);
nc=(1.3354);
rho=(1);
lambda=(532.3);
m=(0);
F = (((2*pi./lambda)*(sqrt(nf^2-neff.^2)*hf))-atan((nf/nc)^(2*rho)*sqrt ((neff.^2-nc^2)/(nf^2-neff.^2)))-atan((nf/ns)^(2*rho)*sqrt ((neff.^2-ns^2)/(nf^2-neff.^2))) -(m*pi));% equation 8 from paper
end

[Stephen23]

"Here is the corrected code.."

Note that this code completely ignores the values of hf defined on the first line. I doubt that is the intent.