How do I solve this error?

Question

0 个投票

My teacher put in (from what I can tell) an identical code but I can't get it working. Can somebody help me make it work and explain the error?

n1 = 1; %utanför linsen
n2 = 1.5; %i linsen
D = 10; %linsens diameter (cm)
R = D./2; %linsens radie (cm)
d = 10; %fokallängd (cm)
lopt = n1*sqrt(d.^2 + R.^2); %Optiska vägen då strålen inte bryts i linsen
Y = linspace(0, R, 1000);
X = linspace(0, d, 1000);
for ii = 1:length(Y)
    L1(:,ii) = sqrt( (d-X).^2 + Y(ii).^2)*n1;
    L2(:,ii) = X*n2;
    LoptTemp(:,ii) = L1(:,ii) + L2(:,ii);
    diff(:,ii) = abs(LoptTemp(:,ii) - lopt);
    [difference minIndex(ii)] = min(diff(:,ii));
    x_fit(ii) = X(minIndex(ii));
end
figure
plot(x_fit, Y, 'black');
hold on
plot(x_fit.*-1, Y, 'black');
hold on
plot(x_fit, -Y, 'black');
hold on
plot(x_fit.*-1, -Y, 'black');
hold on
ylim([-max(Y)-3, max(Y)+3]);