The first column of the VAL matrix is the real part and the second column is the complex part of the three eigenvalues. A symmetric example follows: x={1 1,1 2,1 3,1 4}; ... a=eigval(xpx); /* xpx is a ...

Let be the eigenvalues and the normalized eigenvectors of T, i.e. We consider the inverse problem: Determine from and . It is well known that this problem can easily be solved by the Lanczos method.