14.10.2 Examples involving matrices

We illustrate computing with the matrix whose $ i,j$ entry is $ i/j$ , for $ i,j=1,\ldots,4$ .

sage: f = maxima.eval('f[i,j] := i/j')
sage: A = maxima('genmatrix(f,4,4)'); A
matrix([1,1/2,1/3,1/4],[2,1,2/3,1/2],[3,3/2,1,3/4],[4,2,4/3,1])
sage: A.determinant()
0
sage: A.echelon()
matrix([1,1/2,1/3,1/4],[0,0,0,0],[0,0,0,0],[0,0,0,0])
sage: A.eigenvalues()
[[0,4],[3,1]]
sage: A.eigenvectors()
[[[0,4],[3,1]],[1,0,0,-4],[0,1,0,-2],[0,0,1,-4/3],[1,2,3,4]]

We can also compute the echelon form in Sage:

sage: B = matrix(QQ, A)
sage: B.echelon_form()
[  1 1/2 1/3 1/4]
[  0   0   0   0]
[  0   0   0   0]
[  0   0   0   0]
sage: B.charpoly('x').factor()
(x - 4) * x^3

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