Undefined variable problem in a simple model for non-linear oscillator

Hey guys, I'm just trying to run a very simple function to help model a non-linear oscillator. Here's the code:

function vp=F(t,v);

vp=zeros(2,1);

vp(1)=v(2);

vp(2)= -(v(2)+v(1)+3*(v(1))^3)+20*cos(w*t);

I had to transform it into a 1st order eq b/c it seems like matlab can't handle second order equations for some reason. When I type in the following, I get an error saying "undefined function or variable 't'"

%[t,v]=ode45('F',[0,15],[0,0])

plot(t,v(:,1))

I'm not experienced with MatLab at all! Any help would be greatly appreciated.

Answer 1

[Paulo Silva]

"When I type in the following, I get an error saying "undefined function or variable 't'"

%[t,v]=ode45('F',[0,15],[0,0])

plot(t,v(:,1))"

You commented the line where the t was created therefore there's no t and matlab gives you that error

[Matt]

Wow duh! This is what happens when you don't pay attention and neglect sleep. I feel pretty dumb now, but thank you for saving me from going on a witch hunt for that seemingly elusive error. Much appreciated!