# Plot dynamics of an ODE

3 views (last 30 days)
UserCJ on 21 Sep 2022
Commented: Cris LaPierre on 22 Sep 2022
I have an ODE and I need to plot with respect to and varying p. Following is the sample plot required.
I managed to draw one plot for and following is the sample code.
[xi,x] = meshgrid(0:0.001:1,0:0.002:1);
p =1
f2 = @(x,a,b) a*b*(x)./(b-2+x));
f1 = @(x,a,b) a*b*(1-x)./(2*b-x);
rs = @(x1,x2,a,b,p) x1.*f1(x,a,b) - p.*(1-x1).*f2(x,a,b);
figure
contour(x1,2,rs(x1,x2,1,2,1),[0 0]);
Next I added a loop for p as follows:
np = 10;
phi = linspace(0,1,np);
for p = 1:np
f2 = @(x,a,b) a*b*(x)./(b-2+x));
f1 = @(x,a,b) a*b*(1-x)./(2*b-x);
rs = @(x1,x2,a,b,p) x1.*f1(x,a,b) - p.*(1-x1).*f2(x,a,b);
R = rs(x1,x2,1,2, p(p));
contour(x1,x2,R);
hold on
end
hold off
But, instead of the required ourput of 10 plots in one graph, I get many plots (>10) in my output. Can someone please help me with this?
Cris LaPierre on 21 Sep 2022
Edited: Cris LaPierre on 21 Sep 2022
You have not copied your code correctly here, as both examples do not run.

Cris LaPierre on 21 Sep 2022
I'm assuming your goal is to plot a line for when the function rs is equal to zero for various values of p. You could do that using contour, but I don't think that is the best way. However, you could still use contour to get the (x,y) coordinates of the 0 contour line for each, and then plot those.
np = 10;
[x1,x2] = meshgrid(0:0.001:1,0:0.002:1);
for p = 1:np
f2 = @(x,a,b) a*b*(x)./(b-2+x);
f1 = @(x,a,b) a*b*(1-x)./(2*b-x);
rs = @(xi,x,a,b,p) xi.*f1(x,a,b) - p.*(1-xi).*f2(x,a,b);
R = rs(x1,x2,1,2, p);
figure(1)
M=contour(x1,x2,R,[0 0]);
figure(2)
plot(M(1,2:end),M(2,2:end),'DisplayName',"p="+p)
axis([0 1 0 1])
hold on
end
hold off
legend(Location="northwest")
Cris LaPierre on 22 Sep 2022

### Categories

Find more on Surface and Mesh Plots in Help Center and File Exchange

R2022b

### Community Treasure Hunt

Find the treasures in MATLAB Central and discover how the community can help you!

Start Hunting!

Translated by