MATLAB: Plot lines not showing up

plot lines

clc
clear
format long
R=287;
r=1.4;
Mach=[2:0.5:6];
for i=1:9
    M=Mach(1,i);
   for density=1.225
       To=300;
       p=101325;
       ao=sqrt(r*R*To);
       V=ao*M;
       m=M^2;
       P=p*(((2*r*m)-(r-1))/(r+1));
       D=density*(((r+1)*m)/(((r-1)*m)+2));
       Q=(D*((V^2)/2));
       Po=P+Q;
       plot(Po,P,'r*')
       hold on
   end
   for density=1.203
       To=284.9;
       p=99507.54;
         ao=sqrt(r*R*To);
         V=ao*M;
         m=M^2;
         D=density*(((r+1)*m)/(((r-1)*m)+2));
         Q=D*((V^2)/2);
         P=p*(((2*r*m)-(r-1))/(r+1));
         Po=P+Q;
         plot(Po,P,'ko')
       hold on
   end
end
hold off
xlabel('Po')
ylabel('P')
legend('Wind Tunnel','FL500','Location','northwest')

Best Answer

You can save the generated values into a vector/ matrix and plot at the end. Check the below code: 
clc
clear
format long
R=287;
r=1.4;
Mach=[2:0.5:6];
x = zeros(9,2) ; 
y = zeros(9,2) ; 
for i=1:9
    M=Mach(1,i);
   for density=1.225
       To=300;
       p=101325;
       ao=sqrt(r*R*To);
       V=ao*M;
       m=M^2;
       P=p*(((2*r*m)-(r-1))/(r+1));
       D=density*(((r+1)*m)/(((r-1)*m)+2));
       Q=(D*((V^2)/2));
       Po=P+Q;
       plot(Po,P,'r*')
       hold on
       x(i,1) = Po ;
       y(i,1) = P ; 
   end
   for density=1.203
       To=284.9;
       p=99507.54;
         ao=sqrt(r*R*To);
         V=ao*M;
         m=M^2;
         D=density*(((r+1)*m)/(((r-1)*m)+2));
         Q=D*((V^2)/2);
         P=p*(((2*r*m)-(r-1))/(r+1));
         Po=P+Q;
         plot(Po,P,'ko')
       hold on
       x(i,2) = Po ;
       y(i,2) = P ; 
   end
end
hold off
xlabel('Po')
ylabel('P')
figure
plot(x,y)
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