index must be a positive integer or logical.

%Programme to model Damped free vibration in a cannon %clear Screen clear; %define constants m=500; k=10000; %Evaluate natural frequency wn=sqrt(k/m) %Evaluate natural time period tn=(2*pi)/wn %Enter initial conditions xmax=0.4; %calculate critical damping constant cc=2*m*wn %set initial displacement & velocity xo=0; xdz=xmax*wn*exp(1); z=1.5; %defining constants C1 & C2 C1=(wn(z+sqrt(z^2-1))+xdz)/(2*wn*(sqrt(z^2-1))) C2=(wn(z-sqrt(z^2-1))-xdz)/(2*wn*(sqrt(z^2-1)))

But I'm getting an error Attempted to access wn(2.61803); index must be a positive integer or logical. Error in Cannon2 (line 20) C1=(wn(z+sqrt(z^2-1))+xdz)/(2*wn*(sqrt(z^2-1)))

In the workspace it's calculated at 4.4721 and I've used term wn in previous code and it worked fine without being an integer

Answer 1

[Michael Haderlein]

I dont know how this equation should read, but might there be a * missing? You write

 C1=(wn(z+sqrt(z^2-1))+xdz)/(2*wn*(sqrt(z^2-1)))

but you might mean

 C1=(wn*(z+sqrt(z^2-1))+xdz)/(2*wn*(sqrt(z^2-1)))

Same for C2.

[Gary]

That fixed it, schoolboy error.

Thank you Michael