The roots function calculates the roots of a polynomial:
r = roots(p) r = 2.0946 -1.0473 + 1.1359i -1.0473 - 1.1359i
By convention, the MATLAB® software stores roots in column vectors. The function poly returns to the polynomial coefficients:
p2 = poly(r) p2 = 1 8.8818e-16 -2 -5
poly and roots are inverse functions, up to ordering, scaling, and roundoff error.