MATLAB: 2D array in for loop problem

array

N=40
a=0.9
x =zeros(41,41)
for k=0:N
  for col = 0:41
    for row = 0:41
        x(row,col)=a.^(k+k)*1;
    end
  end
end
What is the problem (error: x(0,_): subscripts must be either integers 1 to (2^31)-1 or logicals)?

Best Answer

Unlike Python, C, C++ and other programming languages, Matlab starts the matrix index with 1 instead of 0.
So just change the first number then it should be working without having error.
N=40
a=0.9
x =zeros(41,41)
for k=1:N
    for col = 1:40
        for row = 1:40
            x(row,col)=a.^(k+k)*1;
        end
    end
end
However, 1st to 39th iteration of k for loop might be overwritten and x would only show the result of 40th iteration of k for loop... And the final result of x would only be a 40-by-40 matrix filled with the value of 0.9^80=2.1847e-4 for all elements...
Which could be simplifed as
N=40
a=0.9
x=a^(2*N)*ones(N)
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