How to add trajectory into a phase plane?
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Hi, I have the code below of my function phase plane and it works fine. I want to add some trajectories into my phase plane, how am I able to do it?
function my_phase()
[~,X] = ode45(@EOM,[0 50],[1 1]);
u = X(:,1);
w = X(:,2);
plot(u,w)
xlabel('u')
ylabel('w')
grid
end
function dX = EOM(t, y)
dX = zeros(2,1);
u = y(1);
w = y(2);
A = 1;
B = 1;
dX = [w*u^2 - B*u;...
A - w - w*u^2];
end
It is my original phase plane
![](https://www.mathworks.com/matlabcentral/answers/uploaded_files/157493/image.bmp)
And I want my phase plane like this:
![](https://www.mathworks.com/matlabcentral/answers/uploaded_files/157495/image.png)
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채택된 답변
Mischa Kim
2014년 2월 24일
편집: Mischa Kim
2014년 2월 24일
Like this?
function my_phase()
IC = [1 1; 1 2;1 3;1 4];
hold on
for ii = 1:length(IC(:,1))
[~,X] = ode45(@EOM,[0 50],IC(ii,:));
u = X(:,1);
w = X(:,2);
plot(u,w,'r')
end
xlabel('u')
ylabel('w')
grid
end
function dX = EOM(t, y)
dX = zeros(2,1);
u = y(1);
w = y(2);
A = 1;
B = 1;
dX = [w*u^2 - B*u;...
A - w - w*u^2];
end
댓글 수: 3
Mischa Kim
2014년 2월 24일
편집: Mischa Kim
2014년 2월 24일
What do you mean by not working correctly? Do you get an error msg, or, the plot does not look like the one you posted for the simple harmonic oscillator?
You only replace the first function, keep the second. See above.
추가 답변 (2개)
Sundas Mustafa
2015년 3월 13일
use Quiver command for phase portrait. educ.jmu.edu/~strawbem/Phase_how_to.pdf
댓글 수: 0
Xiwen Yuan
2014년 11월 5일
편집: Xiwen Yuan
2014년 11월 5일
Hey, i have another answer to replace the first function with the following
function my_phase()
IC = [1 1; 1 2;1 3;1 4];
hold on
for ii = 1:length(IC(:,1))
[~,X] = ode45(@EOM,[0 50],IC(ii,:));
u = X(:,1);
w = X(:,2);
plot(u,w,'r')
u = gradient(X(:,1));
v = gradient(X(:,2));
quiver(X(:,1),X(:,2),u,v);
end
xlabel('u')
ylabel('w')
grid
end
![](https://www.mathworks.com/matlabcentral/answers/uploaded_files/176492/image.png)
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