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Mathematica Numerical Computation

while loop issues

Derek du Plessix

Derek du Plessix, University of Aberdeen

Posted 12 years ago

POSTED BY: Derek du Plessix

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David Keith

Posted 12 years ago

POSTED BY: David Keith

Derek du Plessix

Derek du Plessix, University of Aberdeen

Posted 12 years ago

I realized that the condition which had to be met was: Abs[Y -Y1] < 10^-4, in other words F/Fpr < 10^-4 not Y1 < 10^-4. Thank you, your post was really helpful because now I know a procedure to follow when I need to figure out what's going on. Best regards, Derek du Plessix

POSTED BY: Derek du Plessix

David Keith

Posted 12 years ago

POSTED BY: David Keith

Derek du Plessix

Derek du Plessix, University of Aberdeen

Posted 12 years ago

POSTED BY: Derek du Plessix

Gustavo Delfino

Posted 12 years ago

Inside the while loop, you probably want to replace the double equal signs with single equal signs and put the semicolon and the end of those lines.

POSTED BY: Gustavo Delfino

Derek du Plessix

Derek du Plessix, University of Aberdeen

Posted 12 years ago

gamma = 21/28.96; P = 2000 ; T = 581.67; Tpc = 168 + 325* gamma - 12.5gamma^2; Ppc = 667 + 15gamma - 37.5gamma^2; Tpr = T/Tpc; t = 1/Tpr; Ppr = 2000/Ppc; X1 = -0.06125Ppr t Exp[-1.2* (1 - t)^2] ; X2 = (14.76 t - 9.76t^2 + 4.58t^3); X3 = (90.7 t - 242.2t^2 + 42.4t^3); X4 = (2.18 + 2.82t); Y = 0.0125PprtExp[-1.2(1 - t)^2] F = X1 + (Y + Y^2 + Y^3 + Y^4)/(1 - Y)^3 - X2Y^2 + X3Y^X4 Fpr = (1 + 4Y + 4Y^2 - 4Y^3 + Y^4)/(1 - Y)^4 - 2X2Y + X3X4Y^(X4 - 1) Y1 = Y - F/Fpr While[Abs[Y1] > 10^-4, Y == Y1 F == X1 + (Y + Y^2 + Y^3 + Y^4)/(1 - Y)^3 - X2Y^2 + X3Y^X4 Fpr == (1 + 4Y + 4Y^2 - 4Y^3 + Y^4)/(1 - Y)^4 - 2X2Y + X3X4*Y^(X4 - 1) Y1 == Y - F/Fpr] Y1

gamma = 21/28.96;
P = 2000 ;
T = 581.67;
Tpc = 168 + 325* gamma - 12.5*gamma^2;
Ppc = 667 + 15*gamma - 37.5*gamma^2;
Tpr = T/Tpc;
t = 1/Tpr;
Ppr = 2000/Ppc;
X1 = -0.06125*Ppr *t* Exp[-1.2* (1 - t)^2] ;
X2 = (14.76 *t - 9.76*t^2 + 4.58*t^3);
X3 = (90.7* t - 242.2*t^2 + 42.4*t^3);
X4 = (2.18 + 2.82*t);
Y = 0.0125*Ppr*t*Exp[-1.2*(1 - t)^2]
F = X1 + (Y + Y^2 + Y^3 + Y^4)/(1 - Y)^3 - X2*Y^2 + X3*Y^X4
Fpr = (1 + 4*Y + 4*Y^2 - 4*Y^3 + Y^4)/(1 - Y)^4 - 2*X2*Y + 
  X3*X4*Y^(X4 - 1)
Y1 = Y - F/Fpr
While[Abs[Y1] > 10^-4,
 Y == Y1
   F == X1 + (Y + Y^2 + Y^3 + Y^4)/(1 - Y)^3 - X2*Y^2 + X3*Y^X4
    Fpr == (1 + 4*Y + 4*Y^2 - 4*Y^3 + Y^4)/(1 - Y)^4 - 2*X2*Y + 
   X3*X4*Y^(X4 - 1)
    Y1 == Y - F/Fpr]
Y1

POSTED BY: Derek du Plessix