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1

$0.1$ is not exactly representable in double precision arithmetic, and it will be rounded. The double precision representation of $0.1$ is $\verb|00111111 10111001 10011001 10011001 10011001 10011001 10011001 10011010|,$ which is $0.100000000000000005551115123126$. As you can see, if you compute $h$ by subtracting "$0.1$" from it repeatedly, you ...

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To make my comments more explicit: Try with the following code for the DDE function that eliminates P function dydt = dde(t,y,yd,A) n = length(A); dydt = diag(A).*y; k = 0; for i = 1:n for j = (i+1):n dydt(i) += A(i,j)*yd(j,k); dydt(j) += A(i,j)*yd(i,k); k = k+1; end end end This eliminates the $O(n^3)$ matrix-vector ...

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Let's take it from the beginning. I was unable to run your code as it must be missing some input, but I see that your input to the differential equations is the current $I$ which you control as a user, and it looks something like this: You will notice that this input is discontinuous, and thus non-differentiable. Unfortunately matlab does not have any ...

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The elemental stiffness matrix must be always singular because while deriving it we do not impose any constraints or boundary conditions. Thus inverting the stiffness matrix to solve for displacements/position-vectors/degrees-of-freedom should yield indeterminate results.

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I think that what you are looking for is a Computer Algebra System (CAS). You could find a list in Wikipedia. I don't know which one suits your particular interest, although Singular seems to be a good candidate.

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