Why Does Matlab Say Undefined Function for cldesf in ode23?

[sami23]

I can't recreate a Matlab example on Matlab 7.12.0 that is straight from the book:

How do I call M-function cldesf?

This is the error I get:

>> [t,x]=ode23('cldesf',[t0,tf],x0t,[],A);
? Error using ==> feval
Undefined function or method 'cldesf' for input arguments of type 'double'.

Error in ==> odearguments at 98
f0 = feval(ode,t0,y0,args{:}); % ODE15I sets args{1} to yp0.

Error in ==> ode23 at 171
[neq, tspan, ntspan, next, t0, tfinal, tdir, y0, f0, odeArgs, odeFcn, ...

 

[rsk2mc]

Check to make sure where you saved it is also your working directory