# Plotting and coding problems

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Mark Anthony Manansala on 26 Feb 2022
Answered: Alan Stevens on 26 Feb 2022
Hello, I'm currently creating a code in which it involves a trial and error wherein when abs(Vc-Va) is less than 0.0001 then Vc=V if not then Vc=Va. then I will plot the V (outcome from loop) vs T (from 300-500 with increment of 0.6) and Z(outcome of loop) Vs T.
I'm having a hard time setting up the plot as it shows no graphing
T = 300:0.6:500;
w = 0.224;
Tc = 304.2;
Pc = 73.83;
k = 0.37464+(1.54226*w)-((0.26992)*(w^2));
b = 0.07780*((R*Tc)/Pc);
e = 1 - sqrt(2);
s = 1 + sqrt(2);
for i = 350:0.5:500
Tr = i/Tc;
al = (1+k*(1-(Tr^(1/2))))^2;
a = 0.45724*(((R^2)*(Tc^2)*al)/Pc);
Va = (R*(i))/P;
Vc = ((R*(i))/P) + b - (a/P)*((Va-b)/((Va+e*b)*(Va+s*b)));
Ab = abs((Vc-Va)/Vc);
while (Ab>0.001)
Va = Vc;
end
V = Vc
Z = ((P*V)/(R*i))
end
x = T';
y = V;
plot(x, y),

Alan Stevens on 26 Feb 2022
More like this perhaps:
T = 300:0.5:500;
w = 0.224;
Tc = 304.2;
Pc = 73.83;
k = 0.37464+(1.54226*w)-((0.26992)*(w^2));
R = 1; %%% You haven't defined R and P, so I've used arbitrary values
P = 10;
b = 0.07780*((R*Tc)/Pc);
e = 1 - sqrt(2);
s = 1 + sqrt(2);
for i = 1:numel(T)
Tr = T(i)/Tc;
al = (1+k*(1-(Tr^(1/2))))^2;
a = 0.45724*(((R^2)*(Tc^2)*al)/Pc);
Va = (R*(T(i)))/P;
Vc = ((R*(T(i)))/P) + b - (a/P)*((Va-b)/((Va+e*b)*(Va+s*b)));
Ab = abs((Vc-Va)/Vc);
if (Ab<0.0001)
Vc = Va;
end
V(i) = Vc;
Z(i) = ((P*V(i))/(R*T(i)));
end
subplot(2,1,1)
plot(T, V)
xlabel('T'),ylabel('V')
subplot(2,1,2)
plot(T, Z)
xlabel('T'),ylabel('Z')