error solving stiff ODE system with ode15s

the "Not enough input arguments" error pops up every time I run my code, the idea is that N is the spatial coordinate, and I am trying to solve the time dependency for every discrete point in space at a time, the equation for each point in space depends on the solutions for all the points before it, here is my attempt at it:

 tspan=[0 logspace(1,5)];
 y0=zeros(length(N));
 [t,y]=ode15s(odelad,tspan,y0);

where odelad is in a separate .m file:

 function dydt=odelad(t,y)
 D0=5.8e-11;
 IUV=1;
 n=30;

 sig_g=1;
 alpha_G=IUV*D0;
 R=3e-17;
 N=logspace(17,23);
 for i=1:length(N)
     N_(i)=n*sum(y(1:i));
 end
 dydt=(R*n).*(1-2.*y)-(alpha_G/2).*f_DB96(N_)*exp(-sig_g.*N);

also f_DB96(N) is a separate function saved in the same folder, but it didn't even get that far and the erorr I keep getting:

 Not enough input arguments.
 Error in odelad (line 11)
     N_(i)=n*sum(y(1:i));
 Error in tester (line 27)
 [t,y]=ode15s(odelad,tspan,y0);

help please !

Answer 1

[Walter Roberson]

Change to

 [t,y]=ode15s(@odelad,tspan,y0);

[Jan]

@Elad Oz: If this is not clear immediately: Your code ode15s(odelad,tspan,y0) includes a call of the function odelad() without input arguments, while Walter's code provides a handle to the function as 1st input to ode15s. The error message mentions the problem clearly and you can use the debugger to find the reason by your own: Set a breakpoint in the failing line and type in the input arguments in the command line, until you understand, what's going on.

[Elad Oz]

understood, thank you both ! In my search for an answer i did come across the concept of a function handle but couldnt really understand what it is, I also found out putting the name of the function as a string also works. Could you maybe give a little explanation as to what a function handle is and if there is a connection to the fact that a string also worked or is that just another form of input the function accepts?