Need help resolving error "Index exceeds matrix dimensions"

Question

Amanda Lococo 2018-4-6

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https://ww2.mathworks.cn/matlabcentral/answers/393153-need-help-resolving-error-index-exceeds-matrix-dimensions

关闭： MATLAB Answer Bot 2021-8-20

I keep getting this error when trying to run my code, but I'm not sure how to resolve it. Here is the error I'm getting:

"Index exceeds matrix dimensions.

Error in code>@(x)([exp(im*k(j,1)*x(j,1)),0;0,exp(-im*k(j,1)*x(j,1))])

Error in code (line 57)

C = C(x);

Thanks in advance!

clear all;
format long;
im = sqrt(-1);
CellLength = 1;
ibeta = 1;
%Define materal properties 
CellLength = 1;
layers = 2;
d = [0.4;0.6];
dTotal = d(1,1)+d(2,1);
xc = [0;0.4];
Ef = 12;
pf = 3;
cf = sqrt(Ef/pf);
Em = 1;
pm = 1;
cm = sqrt(Em/pm);
w = 5;
T1 = [cos(.2*w) (1/(6*w))*sin(.2*w); -6*w*sin(.2*w) cos(.2*w)];
T2 = [cos(.6*w) (1/w)*sin(.6*w); -w*sin(.6*w) cos(.6*w)];
T = T2*T1;
Z1 = 6*w;
Z2 = w;
Z = [Z1;Z2];
%Solve eigenvalue problem for k
[V,D] = eig(T);                 %D = eigenvalues, %V = eigenvectors
k1 = log(D(1,1))/(im*dTotal);
k2 = log(D(2,2))/(im*dTotal);
k = [k1;k2];
for j = 1:layers
    B = @(j)([1 1; im*Z(j,1) -im*Z(j,1)]);
    B = B(j);
    C_a = @(j)([exp(im*k(j,1)*xc(j,1)) 0; 0 exp(-im*k(j,1)*xc(j,1))]);
    C_a = C_a(j);
      if j == 1
          a = (inv(B)*V(:,1));
          alpha = a;
          beta = B;
      else
          a = inv(C_a)*inv(B)*T*beta*alpha;
      end
      for x = 0:0.1:5
          C = @(x)([exp(im*k(j,1)*x(j,1)) 0; 0 exp(-im*k(j,1)*x(j,1))]);
          C = C(x);
          y = @(x)(B*C*a);
          y = y(x);
      end
  end

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Answer 1

Andrew Davies 2018-4-6

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此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/393153-need-help-resolving-error-index-exceeds-matrix-dimensions#answer_313818

Your problem is that the loop starts with x=0. You then try to access C(x). Arrays start indexing at 1 in MATLAB, so you can't have the zeroth element. Hence the error.