I am getting Vectors must be the same length error when I tried to plot. I have attached the full Matlab-files.

 zspan=[0,400];
w0=0.1;
b=1;
gmark=1;
y0=[b*b*w0; b*b*w0*w0; b*b*w0*gmark];% Initial values 
options=odeset('RelTol',1e-6,'AbsTol',1e-6,'Events',@stopevents);
 sol=ode45(@rhs,zspan, y0,options);
sol.mssflx=sol.y(1,:);
sol.vel=sol.y(2,:)./sol.mssflx;
sol.gmark=sol.y(3,:)./sol.mssflx;
sol.b=sqrt(sol.mssflx./sol.vel);
sol.mntflx=sol.mssflx.*sol.vel;
sol.bncyflx=sol.mssflx.*sol.gmark;
figure(1)
plot(sol.vel,zspan)
%%%%%
function dy=rhs(z,y)
% Calculate rho and N2(z)
[rho, Nsqr]=density1(z);
% Calculate entrainment
alpha=0.116;
massflux=y(1);
velocity=y(2)/massflux;
gmark=y(3)/massflux;
fric= 1*velocity*abs(velocity);
b=sqrt(massflux/velocity);
dy(1)=2*alpha*b*velocity;
dy(2)=b*b*gmark- fric;
dy(3)=-massflux*Nsqr;
dy=dy';
end

Answer 1

[Matt J]

In,

plot(sol.vel,zspan)

zspan only has two numbers in it. sol.vel has more. So, they cannot be sensibly plotted together.

[Dereje]

oh yes, Now I get it. Thanks for the help.

[Dereje]

To add one thing, how can I stop the ode at a certain value? One of the results in the above code is going to infinity and I wanted to stop it at some level.

[Dereje]

I am getting this error : Undefined function 'sign' for input arguments of type 'logical'.

[Walter Roberson]

stopevents needs to return a numeric value, not a logical. Confusingly, the numeric value should be less than or equal to 0 to signal continuation, and greater than 0 to signal termination.