Vectors must be the same lengths

Hi there, I made equation with the Euler method and the Heun method. For an assignment I have to compare these two graphs. The problem is, when I take step size "dt=0.02" everything is okay.

But I also need graphs with stepsize "dt=0.2" and an error came up: "Vectors must be the same lengths"

Here is my m-file:

m=21974;
k=87896;
c=54935;
dt=0.2;
t= 0:dt:10;
lt=length(t);
y(1)=1;
z(1)=0;
% formula Euler
tic
for n=1:lt-1
y(n+1)=y(n)+(z(n)*dt)*(k/m);
z(n+1)=z(n)-(y(n)+z(n))*dt*(c/m);
end
%plot(t,y);
%plot(t,z);
toc
% formula Heun
for n=1;lt-1
y(n+1)=y(n)+(0.5*(z(n))*(k/m)+y(n+1))*dt;
z(n+1)=z(n)-(0.5*(y(n))*(c/m)+z(n+1))*dt;
end
%plot(t,y);
plot(t,z);

I hope you guys can figure it out. None of my teachers are available right now.

Answer 1

[Mischa Kim]

Daan, turn the script into a function and you should be good. As the first line in your code, add

 function myEuler()  % or some other function name

and end the function with the end statement:

 end

Save the file under the same name as your function ( myEuler.m in my case).

Answer 2

[Daan]

Thank you it worked!