Using variable legend in a for loop

Hii,

So while using variable legend code, the color of curves and that of legend are mismatching. And when y = 0, there is a colored line which is coming out of nowhhere. Can anybody be kind enough to help?

n0 = 1;

lam = 3:0.01:7;

a1 = 3.263;

b1 = 0.1644;

n1 = sqrt(1 + (a1.*(lam.^2))./((lam.^2) - (b1^2)));

ns = 1.5;

th = 0;

ii = 1;

for k = 3:1:7

d1 = k./(4*(2.06));

for j = 1:numel(lam)

phi1 =2*pi.*(d1./lam).*sqrt((n1).^2 - sind(th).^2);

D0 = [1 1; n0 -n0];

D_0 = inv(D0);

D1 = [1 1;n1(j) -n1(j)];

D_1 = inv(D1);

Ds = [1 1;ns -ns];

P1 = [exp(1i.*phi1(j)) 0; 0 exp(-1i.*phi1(j))];

M = D_0*D1*P1*D_1*Ds;

r(j,k) = M(2,1)./M(1,1);

R(j,k) = abs(r(j,k).^(2));

end

leg_str{ii} = ['k = ' num2str(k)];

ii = ii + 1;

plot(lam,R,LineWidth=2);

hold on;

end

legend(leg_str);

Answer 1

[VBBV]

n0 = 1;
lam = 3:0.01:7;
a1 = 3.263;
b1 = 0.1644; 
n1 = sqrt(1 + (a1.*(lam.^2))./((lam.^2) - (b1^2)));
ns = 1.5;
th = 0;
ii = 1;
for k = 3:1:7
d1 = k./(4*(2.06));
      for j = 1:numel(lam)
phi1 =2*pi.*(d1./lam).*sqrt((n1).^2 - sind(th).^2);
        D0 = [1 1;  n0 -n0];
        D_0 = inv(D0);
        D1 = [1 1;n1(j) -n1(j)];
        D_1 = inv(D1);
        Ds = [1 1;ns -ns];
        P1 = [exp(1i.*phi1(j)) 0; 0 exp(-1i.*phi1(j))];
         M = D_0*D1*P1*D_1*Ds;
        r(j,k-2) = M(2,1)./M(1,1);
        R(j,k-2) = abs(r(j,k-2).^(2));
      end
     
     leg_str{k-2} = ['k = ' num2str(k)];
     
    plot(lam,R(:,k-2),LineWidth=2);
    hold on;
end
legend(leg_str);

[VBBV]

The below lines in your code needs a change, since for loop for the r(j,k) and R(j,k) matrices with index k begins at 3 and ends at 7. Matlab considers (computes) preceding elements i.e. 1 to 2 as zeros for those matrices.

So, when plotting the graph, it is treated as zeros, and corresponding legend is displayed for zeros.

r(j,k-2) = M(2,1)./M(1,1);
R(j,k-2) = abs(r(j,k-2).^(2));

[Ashi Khajotia]

thanks a lot for your help!!