In spite of being real, I get the error: Warning: Imaginary parts of complex X and/or Y arguments ignored.

Hi every one. I have a system of ODE. My solution is real (isreal (A_ODE)=1), but I get this error: Warning: Imaginary parts of complex X and/or Y arguments ignored. Actually I expected the steady- state soIution but I got unstable system. I dont know, is this error massage affected on the answer or not I attached the code and really appreciate any help.

thanks in advance

LaserODE

Warning: Imaginary parts of complex X and/or Y arguments ignored.

Warning: Imaginary parts of complex X and/or Y arguments ignored.

Warning: Imaginary parts of complex X and/or Y arguments ignored.

Answer 1

[Walter Roberson]

dNis = Nis - Nth;
Ais = sqrt((AInj^2 - gammaN/gammaP*dNis)/(1 + g*dNis/gammaP));

dNis is negative.

That makes the numerator for the next line a value minus a negative value, which is positive, so the numerator is okay.

But with dNis being sufficiently negative, the denominator is negative, so overall you are taking square root of a negative value.

phi_Tr = zeros(size(A_Tr));

You do not assign any other value to phi_Tr, so phi_Tr is all zero at the time you semilogy(), which means you are trying to plot the log of 0.

[raha ahmadi]

Thank you @Walter Roberson for your help. you are right but I changed semilogy to plot and more important point : I got this error for line 93 ,..,. Ais is initial value. Also, A_ODE, phi_ODE and N_ODE are real. I dont expect something like that. thank you again, I didnot think anyone would read

[raha ahmadi]

I know from the steady state solution and physics of the problem that phi must be limited on the set:

. It seems I must impose this constraint on the solution

[raha ahmadi]

Dear @Walter Roberson

The problem is solved. these lasers after injection experience non stable situations. I tried to impose constraints on phi, but I couldnt. In steady state solution after calculation we choose between the answers and choose those satisfy the physical conditions. I try to repeat this strategy hear but nothing happens. I changed one key parameter (rInj) and reach the answer.

again very thanks for your help

with the best wishes