MATLAB: Tried solving the following complex equation for W varying values of k from 0.1 to 100 and plot the positive imaginary part of the solution (W) against k. Got wrong roots using roots command : S.*((W.^2)​-(C1+C2).*​W.*k+C1.*C​2.*(k.^2))​+i.*(W-C0.​

complexquadraticroots

C1=2 C2=1 C0=2.5 S=2.18e-7 for k=0.1:1:100 C(1)=S; C(2)=(-S.*(C1+C2).*k+i); C(3)=(S.*C1.*C2.*k3-i.*C0.*k); r=roots(C) imagr=imag(r) maxr=max(imagr) plot(k,maxr) end

Best Answer

Alexey, use
 C1 = 2; C2 = 2.5; C0 = 0; S = 2.18e-7;
 k  = 0.1:1:100;
 for ii = 1:numel(k) 
    C(1)=  S; 
    C(2)= -S*(C1+C2)*k(ii) + 1i; 
    C(3)=  S*C1*C2*k(ii)^2 - 1i*C0*k(ii); 
    r        = roots(C);
    imagr    = imag(r); 
    maxr(ii) = max(imagr); 
 end
 plot(k,maxr)
Note: I have not double-checked the coefficients.
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