Plotting issue, not defined parameter?

I have made this script
when I try to plot it I get a message saying S is not identified, I am sure I am doing everything correct. Can anyone help?
here is my script

function Sdot= f3(S,t)
Sdot=zeros(1,2)
K=1
k1=20
k2=5
k3=5
k4=5
k5=2
n=4
s1=1
s2=2

sdot1=k1/(1+(s2/K)^n )-(k3+k5)s1;
sdot2=k5
s1-k4*s2+k2;
endfunction

and in another editor

t=linspace (0,25,2501)
S0=[0; 0];
lsode( “f3” , S0 , t)
plot (t,S(:,1))

any help more than appreciate it

In f3.m, Sdot is always 0. You have to add

Sdot = [ sdot1; sdot2 ];

at the end of the script.
And in the main simulation script, S is never defined. You have to use

S = lsode( "f3" , S0 , t)