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!

Answer 1

[Star Strider]

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

.

[Walter Roberson]

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.