Eigenvectors and the null function

I have a matrix D and I want to find eigenvectors using the null-function and known eigenvalues:

D = [2    -1;
    -1     3];
eigs = eig(D);
q1 = null(D-eigs(1)*eye(2)) %first eigenvector
q2 = null(D-eigs(2)*eye(2)) %second eigenvector

The answer I get is 2×0 empty double matrix, however the eigenvectors should be

[q,l] = eig(D_tilde)

>> q =

   -0.8507   -0.5257
   -0.5257    0.8507

How do I get those values of eigenvectors?

Answer 1

[Christine Tobler]

I'm getting those two eigenvectors when I copy your code into MATLAB:

>> D = [2    -1;
    -1     3];
eigs = eig(D);
q1 = null(D-eigs(1)*eye(2)) %first eigenvector
q2 = null(D-eigs(2)*eye(2))
q1 =
    0.8507
    0.5257

q2 =
    0.5257
   -0.8507   

But round-off errors can change between different versions and machines. Try passing a different tolerance as the second input to null, that should allow it to find an output x = null(M) even if M*x is larger than the default tolerance.