Assigning variable names to eigenvalues

In MATLab,
I am unsure how to take the output from an eigenvalue calculation to then use in another calculation.
For example I input
A = [1 2 3; 1 2 3; 1 2 3];
L = eig(A)
%This is where i need to assign variable names to the eigenvalues returned and order them from largest to smallest.
Thanks!

回答(1 个)

Just subscript the original vector to refer to them individually —
format long G
A = [1 2 3; 1 2 3; 1 2 3];
L = eig(A)
L = 3×1
5.99999999999999 -4.46188628311578e-16 -5.6378189834996e-18
format short
L(1)
ans = 6.0000
L(2)
ans = -4.4619e-16
L(3)
ans = -5.6378e-18
.

1 个评论

You could proceed to
E1 = L(1);
E2 = L(2);
E3 = L(3);
but then when you went to order them, it would be far easier to use
sorted_eig = sort(L,'descend')
than it would be to use
if E1 >= E2
if E1 >= E3
sorted_eig = [E1, E2, E3];
else
sorted_eig = [E3, E1, E2];
end
else
... and more tests
end
Putting them into individual variables is Not Helpful for this purpose.

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