How to add trajectory into a phase plane?
显示 更早的评论
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
And I want my phase plane like this:
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采纳的回答
Mischa Kim
2014-2-24
编辑：Mischa Kim
2014-2-24
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
3 个评论
Alex
2014-2-24
Mischa Kim
2014-2-24
编辑：Mischa Kim
2014-2-24
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.
Alex
2014-3-11
Hey is me again, I have successfully to plot the graph, but it seems like the graph only shows the positive value, and I wonder can the trajectories toward to negative as well. Also I wonder how to add those blue arrow in my phase plane?
更多回答（2 个）
Sundas Mustafa
2015-3-13
1 个投票
use Quiver command for phase portrait. educ.jmu.edu/~strawbem/Phase_how_to.pdf
Xiwen Yuan
2014-11-5
编辑：Xiwen Yuan
2014-11-5
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
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