How to find eigen vectors?

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Sandy
Sandy on 4 Dec 2015
Answered: Marc on 5 Dec 2015
I am using:
A= [-5, 2; 2, -2];
[EigVec, EigVal] = eig(A)
If I use Wolfram, I obtain Eigen Vectors = [1,2;1, -0.5]. Similarly, how can I get MatLab to scale it to 1?
  1 Comment
John D'Errico
John D'Errico on 5 Dec 2015
Edited: John D'Errico on 5 Dec 2015
I answered this identical question before. You cannot get MATLAB to magically scale them as you desire. However, you can DIVIDE EACH VECTOR BY THE FIRST ELEMENT OF THAT VECTOR. Just do the scaling yourself. Take care that the first element is not zero.

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Answers (1)

Marc
Marc on 5 Dec 2015
I love questions like this... As I am always confused?
Maybe it is the way you are setting it up in Wolfram but if you have the symbolic toolbox in Matlab you can use this....
>> A= sym([-5 2; 2 -2])
A =
[ -5, 2] [ 2, -2]
>> [EigVec, EigVal] = eig(A)
EigVec =
[ -2, 1/2] [ 1, 1]
EigVal =
[ -6, 0] [ 0, -1]
So you get something close to what you wanted?
Try something like this in Maple....
A := Matrix([[-5, 2], [2, -2]])
Eigenvectors(A)
Vector(2, {(1) = -1, (2) = -6}), Matrix(2, 2, {(1, 1) = 1/2, (1, 2) = -2, (2, 1) = 1, (2, 2) = 1})
So Matlab's Symbolic toolbox and Maple are reversing the signs which I don't think is a big deal and of course they put things in different spots... Again not a big deal but it just makes you wonder? Or not.

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