How to extract only the real roots of a cubic equation

I am resolving a cubic virial equation of state with a root method in 3 loops for (for Pressure, Temperature and type of Gas). So I have complexe and real solutions. I want, though, only the real ones. Here is the part of the code that doesn't work.

........

for j=1:numel(P)

coef1(i,j,k)=(Rg*T(i))/(P(j))

coef2(i,j,k)=(B2(i,k))*((Rg*T(i))/(P(j)));

coef3(i,j,k)=(B3(i,k))*((Rg*T(i))/(P(j)));

racines{i,j,k}=((roots([coef3(i,j,k), coef2(i,j,k), coef1(i,j,k), -1])));

imagi{i,j,k}=imag(racines{i,j,k})

vraiRacines{i,j,k}=racines{imag(racines{i,j,k})==0}

celldisp(vraiRacines)

end

end

end

This gives:

vraiRacines{2,1,1} =

-8.3654e+04

5.4637e+01

vraiRacines{3,1,1} =

-8.3654e+04

5.4637e+01

vraiRacines{1,2,1} =

-8.3654e+04

5.4637e+01

vraiRacines{2,2,1} =

-8.3654e+04

5.4637e+01

vraiRacines{3,2,1} =

-8.3654e+04

5.4637e+01

So it actually extracts the real solutions but it gives the same real value for all {i,j,k}.... 5.4637e+01.

So I think it enters the loop once and then does the same thing for all i,j and k...

Would you have a solution for me please?