Sort numbers into complex conjugate pairs.
Y = CPLXPAIR(X) rearranges the elements of vector X so that
complex numbers are collected into matched pairs of complex
conjugates. The pairs are ordered by increasing real part.
Any purely real elements are placed after all the complex pairs.
Y = CPLXPAIR(X,TOL) uses a relative tolerance of TOL for
comparison purposes. The default is TOL = 100*EPS .