I have a problem with ode solvers for 3 ode.

I write my 3 ode's and I want to plot a maximum point for each value of "a", I've done a similar problem and it worked, but in this one I have the following errors:

Warning: Failure at t=2.599899e+00.  
Unable to meet integration tolerances without reducing the step size below the smallest value allowed (7.105427e-15) at time t. 
> In ode45 (line 308)   
In Untitled (line 9) 
Index exceeds matrix dimensions.
Error in Untitled (line 12)
if ( (x(n,1) > x(n-1,1)) && (x(n,1) > x(n+1,1)) )

(I have the same error for ode15s)

I don't know what's wrong, here is the following code with the equations:

 clear all 
t0=0;
a=[0];
k=1;
i=1;
for a=-2:0.1:2
f = @(t,x) [x(2);x(3);-x(2)+3*x(2)*x(2)-x(1)*x(1)-x(1)*x(3)-a];
[t,x] = ode45(f,[t0:0.01:300],[0.51 0.51 0.51]);
for n=25000:1:30000
if ( (x(n,1) > x(n-1,1)) && (x(n,1) > x(n+1,1)) )
  plot (x(n,1), a, '.')
  hold on
n=n+1;
end  
end
end

Answer 1

[Torsten]

ode45 has problems to integrate your system of ODEs for a certain a-value.

That's why x has dimension smaller than 30001, and you get the "Index exceeds matrix dimensions" error.

Best wishes

Torsten.