Need help in generating plot in while loop for Buckley Leverett code.

Hello, I'm trying to develop a code for the Buckley Leverett equation. I used a while loop to find the tangent point between the curve and tangent line by equating them to one and then subtracting one. The program is computing the correct values, however, it is not able to plot the graph (S-curve with a tangent line to it). A plot pops up with correct axis values but there is no graph. I'm assuming it's because it's graphing only one point because the while loop keeps iterating over it. I already tried hold on, and drawnow, but it was futile. I have included the code below. Any suggestions and thoughts are more than welcomed, thank you.

%Buckely Leverett Plot 
clear all 
clc
hold on
W=500; %ft
T=25; %ft
L= 1000; %ft 
Por =0.18;
Permb= 50; %md base permeability
Sor=0.3;
Viscw= 1 %cp water viscosity
ViscO= 1.62 ; %cp
qi = 200; %B/D
Swi=0.3
Sw =.4
Swd=(Sw-Swi)/(1-Sor-Swi)

Krw= 0.248*Swd.^2.33
Kro=0.402*(1-Swd).^(2.06)
A=Viscw*Kro
B=ViscO*Krw

C= A/B
fw = 1/(1+((Viscw*Kro)/(ViscO*Krw)))+.1
fw2 =  1/(1+((Viscw*Kro)/(ViscO*Krw)))

% Slope1 = (fw - 0)/(Sw-Swi)
% Slope2 = (fw-fw2)/.0001

%fw= 1/(1+((Viscw*Kro)./(ViscO*Krw)))

while (fw/(Sw-Swi))/((fw-fw2)/.00001) - 1 <= .0001
    %output(fw)
    Slope1 = (fw - 0)/(Sw-Swi)
    Slope2 = (fw-fw2)/.0001

      Sw = Sw+.0001
      Sw2 = Sw-.0001
      Swd=(Sw-Swi)/(1-Sor-Swi);
      Swd2 = (Sw2-Swi)/(1-Sor-Swi);
      Krw= 0.248*Swd^2.33
      Krw2= 0.248*Swd2^2.33;
      Kro=0.402*(1-Swd)^(2.06)
      Kro2=0.402*(1-Swd2)^(2.06);

      fw= 1/(1+((Viscw*Kro)/(ViscO*Krw)));
      fw2=  1/(1+((Viscw*Kro2)/(ViscO*Krw2))); 
      plot(Sw,fw,'r-')
      drawnow
  end

Answer 1

[KSSV]

Replace

   plot(Sw,fw,'r-')

with

plot(Sw,fw,'.r')

[KSSV]

And the better code would be:

%Buckely Leverett Plot
clear all
clc

W=500; %ft
T=25; %ft
L= 1000; %ft
Por =0.18;
Permb= 50; %md base permeability
Sor=0.3;
Viscw= 1 ; %cp water viscosity
ViscO= 1.62 ; %cp
qi = 200; %B/D
Swi=0.3 ;
Sw =.4 ;
Swd=(Sw-Swi)/(1-Sor-Swi) ;
Krw= 0.248*Swd.^2.33 ;
Kro=0.402*(1-Swd).^(2.06) ;
A=Viscw*Kro ;
B=ViscO*Krw ;
C= A/B ;
fw = 1/(+((Viscw*Kro)/(ViscO*Krw)))+.1 ;
fw2 =  1/(1+((Viscw*Kro)/(ViscO*Krw))) ;
% Slope1 = (fw - 0)/(Sw-Swi)
% Slope2 = (fw-fw2)/.0001
%fw= 1/(1+((Viscw*Kro)./(ViscO*Krw)))
count = 0 ;
x = [] ; y = [] ;
while (fw/(Sw-Swi))/((fw-fw2)/.00001) - 1 <= .0001
    count = count+1 ;
    %output(fw)
    Slope1 = (fw - 0)/(Sw-Swi) ;
    Slope2 = (fw-fw2)/.0001 ;
    Sw = Sw+.0001 ;
    Sw2 = Sw-.0001 ;
    Swd=(Sw-Swi)/(1-Sor-Swi);
    Swd2 = (Sw2-Swi)/(1-Sor-Swi);
    Krw= 0.248*Swd^2.33 ;
    Krw2= 0.248*Swd2^2.33;
    Kro=0.402*(1-Swd)^(2.06) ;
    Kro2=0.402*(1-Swd2)^(2.06);
    fw= 1/(1+((Viscw*Kro)/(ViscO*Krw)));
    fw2=  1/(1+((Viscw*Kro2)/(ViscO*Krw2)));
    x(count) = Sw ;
    y(count) = fw ;
end
plot(x,y,'r')

[Nadia Menouar]

Hey, thanks a lot for the quick response and the better code! So the key is using the count method. May I ask why the use of empty brackets before the loop? Thanks

[KSSV]

Actually it is not needed...For the present code. And thanks is accepting the answer.