You can do this without using a for loop:
er=2.2;h=0.1588;
freq={11 2 3 4 5 6 7 8 9 10};
i=1:1:length(freq);
lambda_o=30.0./i ;
ko=2.0*pi./lambda_o;
F=8.791./(i*sqrt(er));
a=F./sqrt(1+2*h./(pi*er*F).*(log(pi*F./(2*h))+1.7726));
ae=a.*sqrt(1+2*h./(pi*er*a).*(log(pi*a/(2*h))+1.7726));
t=linspace(0,pi/2,length(freq));
x=ko.*ae.*sin(t);
j0=besselj(0,x);
j2=besselj(2,x);
j02p=j0-j2;
j02=j0+j2;
grad=(ko.*ae).^2/480*sum((j02p.^2+(cos(t)).^2.*j02.^2).*sin(t).*0.001);
plot(ae,grad);
xlabel('ae->');ylabel('grad->');
If you want to use for loop:
er=2.2;h=0.1588;
freq={11 2 3 4 5 6 7 8 9 10};
for i=1:1:length(freq)
lambda_o=30.0/i ;
ko=2.0*pi/lambda_o;
F=8.791/(i*sqrt(er));
a=F/sqrt(1+2*h/(pi*er*F)*(log(pi*F/(2*h))+1.7726));
ae(i)=a*sqrt(1+2*h/(pi*er*a)*(log(pi*a/(2*h))+1.7726));
t=(0:0.001:pi/2);
x=ko.*ae(i).*sin(t);
j0=besselj(0,x);
j2=besselj(2,x);
j02p=j0-j2;
j02=j0+j2;
grad(i)=(ko*ae(i))^2/480*sum((j02p.^2+(cos(t)).^2.*j02.^2).*sin(t).*0.001);
end
plot(ae,grad);
xlabel('ae->');ylabel('grad->');
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Happy New Year!
