MATLAB: How to plot ODE function and I don’t get this plot.

ode45ode45 function

Best Answer

Solve the ODEs using ODE45, e.g., and use "plot3" for the plot.

Best wishes

Torsten.

Related Solutions

MATLAB: Changing a parameter in a differential equation

Hi Sean,

you can pass the value of epsilon into the ode function with

[tSol,YSol]=ode45(@(t,Y) quantumsystem(t,Y,epsilon),tRange,Y0);

and

function dYdt = quantumsystem(t,Y,epsilon);
    x=Y(1);
    y=Y(2);
    z=Y(3);
    gamma=1/2;
    c=1;
    dtheta=gamma*c/(t^2 + c^2);
    dxdt=(-1/epsilon)*y - dtheta*z; 
    dydt=(1/epsilon)*x;
    dzdt=dtheta*x;
    dYdt=[dxdt;dydt;dzdt];
end

Since ode45 picks the time increments, different values of epsilon may lead to different lengths of tSol and YSol, but the information is there. One of the easier ways to deal with that issue is to set up a for loop with different values of epsilion and use

plot(tSol,z)
hold on

inside the loop as you are doing, only without the color specification.

MATLAB: How to change the options in the figure of z-axis

function main
%Set initial values for r, theta,  z
r00 = 10;
theta00 = 0;
z00 = 1.0;
y0 = [r00 theta00 z00];
% Set model parameters
z0 = 0.0;
a = 0.2;
gamma_inf = 1000.0;
nu = 1.3;
% Set integration period
tspan = 0:0.001:10;
% Call integrator
fun = @(t,y)[-a*y(1);gamma_inf/(2*pi*y(1)^2)*(1-exp(-a*y(1)^2/(2*nu)));2*a*(y(3)-z0)];
[T Y] = ode45(fun,tspan,y0);
R = Y(:,1);
THETA = Y(:,2);
Z = -Y(:,3);
[x y] = pol2cart(THETA,R);
h=plot3(x,y,Z,'r', 'LineWidth', 1')
hold on;
plot3 ([0,0],[0,0],[Z(end),0],'--b')
grid on
xlabel x-axis
ylabel y-axis
zlabel z-axis
zticklabels({'0','10','20','30','40','50','60'})
set(h,'Zdir','reverse')
hold off

Best Answer

Related Solutions

MATLAB: Changing a parameter in a differential equation

MATLAB: How to change the options in the figure of z-axis

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