POLPHASE * Purpose: Phase plot of a continuous-time polynomial * Syntax: POLPHASE(P) * Description: cf. the on-line help * Example With the instruction polphase(1+5*s+10*s^2+10*s^3+5*s^4+s^5)} we obtain a phase plot intersecting the real and imaginary axes 5 times. Moreover its argument is strictly increasing. Consequently, the input polynomial is stable. Now suppose that q=0.5. With the instruction polphase(1+5*s+10*s^2+10*s^3+0.5*s^4+s^5)} we obtain a phase plot intersecting the real and imaginary axes 3 times, so the input polynomial is not stable. * Algorithm: The phase plot is computed by evaluating the input polynomial at 1000 equidistant points along the imaginary axis. The maximum frequency is set to twice the maximum modulus of the roots of the even and odd parts of the input polynomial. To improve readability of the phase plot, the modulus is scaled at the power 1/d where d is the degree of the input polynomial. * Diagnostics: The macro produces error messages if . the input polynomial is constant (zero degree) . the input polynomial is discrete-time * See also: ISSTABLE