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Index exceeds the number of array elements (1) Issue

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Sierra Rezell
Sierra Rezell on 4 Dec 2020
Commented: Sierra Rezell on 4 Dec 2020
I keep getting the error "Index exceeds the number of array elements (1)". The error starts at the line with NX1=. I have no idea how to fix this. The goal is to iterate n and m values to find when NX1 is at a minimum
D = zeros(3,3);
D = D + 1/3*Qbar0*(z(2)^3-z(1)^3);
D = D + 1/3*Qbar0*(z(3)^3-z(2)^3);
D = D + 1/3*Qbar90*(z(4)^3-z(3)^3);
D = D + 1/3*Qbar90*(z(5)^3-z(4)^3);
D = D + 1/3*Qbar0*(z(6)^3-z(5)^3);
D = D + 1/3*Qbar0*(z(7)^3-z(6)^3);
R1 = 0;
for n = 1:10
for m = 1:10;
Nx1(n,m) = (pi^2) * ((D(1,1)*(m/a)^2 + 2*(D(1,2) + 2*D(3,3))*(n/b)^2 + D(2,2)*(n/b)^4 * (a/m)^2)/ (1 + R1((a/b * n/m)^2)))
end
end
min(min(Nx1))

  3 Comments

Star Strider
Star Strider on 4 Dec 2020
This is confusing.
You initially define ‘D’ as a (3x3) matrix (preallocation is the correct approach), then define it as a series of scalars ((1x1) arrays), only the last of which is used, since it over-writes all the previous values. Besides, there are only 6 values of ‘D’ provided, while the original ‘D’ has 9 elements.
Sierra Rezell
Sierra Rezell on 4 Dec 2020
There's more code above that I didn't paste. It's populating D for each stiffness of a compsite lamina layer then adding them together to give me the overall stiffness of the laminate. There are 6 plies. I get a total 3X3 matrix when I run the code. I'm really just intersted in why I keep getting index errors...unless my D is the problem. But, another homework partner wrote the same code for his D matrix and his works
Sierra Rezell
Sierra Rezell on 4 Dec 2020
D =
52.5819141058867 1.54217882265828 0
1.54217882265828 6.38374676045909 0
0 0 2.99475
This is the matrix I get, and according to the cheat code, this is correct. I want to use the D11,D12,D22,D33 values in the formula and only be changing my m and n from 1-10

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Answers (1)

Théophane Dimier
Théophane Dimier on 4 Dec 2020
Have you checked if Nx1 is not already existing before the for loop? It might be that it already exists and that it is a scalar. A hint could be to clear the workspace at the beginning of the code. Anyway, you can trigger "Pause on error" (click on the small arrow under the "Run" button). It will pause the execution right before the error, then launch the code and when it stops, look at the list of variable to check if Nx1 is not just a scalar.

  1 Comment

Sierra Rezell
Sierra Rezell on 4 Dec 2020
Nope, not a scalar. Nx1 can't be calculated because the index exceeds array elements.

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