how to get eigenvalues of a function matrix?

hi

suppose we have with function H=@(x)[x/2,0,0,0;0,-x/2,x,0;0,x,-x/2,0;0,0,0,x/2];

how to get igenvalues and igenvectors of this matrix? eig(H) gives this error ==> Undefined function 'eig' for input arguments of type

'function_handle'.

what i can to do ? plz help me

Answer 1

[Bjorn Gustavsson]

To calculate the eigenvalues of H you have to chose, either to use your implementation where H is a handle to a function returning an ordinary matrix if you feed it an input argument. This for example works fine:

eig(H(3))

Since:

H(3)     

returns a matrix:

ans =

    1.5000         0         0         0
         0   -1.5000    3.0000         0
         0    3.0000   -1.5000         0
         0         0         0    1.5000

That has some eigenvalues. Or you could go with symbolic calculations:

syms x;
eig([x/2,0,0,0;0,-x/2,x,0;0,x,-x/2,0;0,0,0,x/2])