While loop variables are returning NaN ... Why?

Hi, now i understand it is common for NaN to be outoputted when 0 is divided by 0 or inf by inf etc, however i cannot understant why this section of code returns NaN for the variable ew.

Xt and the other following variables produce NaN but this will be because they are a function of ew.

Am I incorrectly using the while loop function

fThetaWater = 2;   
    while 1 
        ew = (1.9226*10^-7*(fThetaWater^4))+(2.4545*10^-5*(fThetaWater^3))+(1.4224*10^-3*(fThetaWater^2))+(0.044436*(fThetaWater))+0.61094;
        Xt = 1+0.622*(Lv/(Patm/Cp))*((ea-ew)/(ThetaAir-fThetaWater));
        ThetaDrop = ThetaAir+((fThetaWater-ThetaAir)*exp(-((6*Nu*Ka)/(rhowater*Cw*(d^2)))*Xt*Tau));
        if abs(fThetaWater-ThetaDrop)<0.00010   
            break;   
        else
            fThetaWater = ThetaDrop;
        end 
    end

[dpb]

fThetaWater = 2; 
b= [1.9226E-7,2.4545E-5,1.4224E-3,0.044436,0.61094]; % ew poly coefficients
while 1 
  ew=polyval(b,fThetaWater);
  Xt = 1+0.622*(Lv/(Patm/Cp))*((ea-ew)/(ThetaAir-fThetaWater));
  ThetaDrop = ThetaAir+((fThetaWater-ThetaAir)*exp(-((6*Nu*Ka)/(rhowater*Cw*(d^2)))*Xt*Tau));
  if abs(fThetaWater-ThetaDrop)<0.00010   
    break;   
  else
    fThetaWater = ThetaDrop;
  end 
end

I'm guessing it's probably other way round -- Xt or ThetaDrop are the culprits and they then propogate to fThetaWater and ew

We don't have the rest of the constants to duplicate but put in an m-file and set

dbstop if naninf

and you'll find who's the first culprit

[Hawki005]

Perfect Thank you!