specfact computes W0 and L such
that W(s)=W0+L*(s*I-A)^-1*B is a
spectral factor of of PHI(s), i.e.
phi(s)=W'(-s)*W(s)
Examples
A=diag([-1,-2]);B=[1;1];C=[1,1];D=1;s=poly(0,'s');W1=syslin('c',A,B,C,D);phi=gtild(W1,'c')+W1;phis=clean(ss2tf(phi))clean(phis-horner(phis,-s)');//check this is 0...[A,B,C,D]=abcd(W1);[W0,L]=specfact(A,B,C,D);W=syslin('c',A,B,L,W0)Ws=ss2tf(W);horner(Ws,-s)*Ws