Function Reference
— Function File: compan (c)

Compute the companion matrix corresponding to polynomial coefficient vector c.

The companion matrix is

               _                                                        _
              |  -c(2)/c(1)   -c(3)/c(1)  ...  -c(N)/c(1)  -c(N+1)/c(1)  |
              |       1            0      ...       0             0      |
              |       0            1      ...       0             0      |
          A = |       .            .   .            .             .      |
              |       .            .       .        .             .      |
              |       .            .           .    .             .      |
              |_      0            0      ...       1             0     _|

The eigenvalues of the companion matrix are equal to the roots of the polynomial.