Spectral radius of 4×4 matrices

I want to find the Spectra redius of the matrices below but I kept running into problem. syms a b c d e f g F = [0 0 0 a; 0 0 0 b; 0 0 0 c; e f g 0]

syms q r s t u V = [q 0 0 0; r s 0 0; 0 0 t 0; 0 0 0 u]

Vi = inv(V) % calculate inverse of V

K = F*Vi % compute the next generation matrix

 eigenvalues= eig(K) % Find the eigenvalues of \(K\)

abs_eigenvalues = abs(eigenvalues) % Compute the absolute values of the eigenvalues.

spectral_radius = max(abs_eigenvalues) %Find the maximum absolute eigenvalue. Error It's show fatal error

Answer 1

[Paul]

Hi Sunday,

The code runs without error (after defining h) here on Answers using 2024b. You're seeing a different result in 2021a?

syms a b c d e f g h % have to define h
F = [0 0 0 a; 0 0 0 b; 0 0 0 c; e f g h]

F = 

syms q r s t u 
V = [q 0 0 0; r s 0 0; 0 0 t 0; 0 0 0 u]

V = 

Vi = inv(V) % calculate inverse of V

Vi = 

K = F*Vi % compute the next generation matrix

K = 

eigenvalues= eig(K) % Find the eigenvalues of \(K\)

eigenvalues = 

abs_eigenvalues = abs(eigenvalues) % Compute the absolute values of the eigenvalues.

abs_eigenvalues = 

spectral_radius = max(abs_eigenvalues) %Find the maximum absolute eigenvalue. Error It's show fatal error

spectral_radius = 

[Sunday Aloke]

Thank you. There no h in the F-matrix.

[Torsten]

There no h in the F-matrix.

The code also works under R2024b if you replace h by 0 in the F-matrix.

Or you could use

spectral_radius = subs(spectral_radius,h,0)

as last command in the code from above.