Extra-diagonal modifications of eigenvalues

The program plots the trajectories of eigenvalues of a matrix from its diagonal

(This program is just a particular case of the more genereal program "Trajectories of eigenvalues".)

(the comments in the program are in italian, i'm sorry)

The program take as input the matrix A and an integer T. T define the accuracy of the plot. The program decompose A as A=D+E where D is the diagonal matrix of the diagonal entries of A, and E is the matrix of extradiagonal elements of A.
The program plot the aigenvalues of the matrices D+tE with t=n/T (n=0,1,2,...,T).