Hi, thanks for getting back to me - sorry, below is the problem (ode) along with initial conditions (ics) and my leading order term in the expansion of u by the method of multiple scales (u0) :

I need to plot a phase portrait of u' against u, using the above multiple scales solution.

Hope that makes sense.  Any further questions, please let me know.

Many thanks in advance

p.s. I've tried DEtools, but it doesn't seem to  like the fact that I'm plotting the ODE but the above mentioned u0.

Thanks for that Doug - I have sent you an email regarding the specifics of that problem.

However, the second, similar problem I mentioned was not knowing how to stop a for-loop when a definition within that for-loop reached a specific value, take for example the loop below, how do I get it to stop when a[i+1]=0.  I don't know which iteration (or i) this will be on, I just know that I need the for-loop to stop when a[i+1]=0.

for i from 0 to 2 do
       a[i+1]:=subs(z1=x[i+1][1],z2=x[i+1][2],z3=x[i+1][3],G):
end do:

For info:
fnctn:=3/2*(z1^2+z3^2)+2*z2^2+z1*z3+2*z2*z3-10*z3;
G:=<diff(fnctn,z1),diff(fnctn,z2),diff(fnctn,z3)>;
and x[i+1] will be given.

Any ideas are greatfully received.

Thanks in advance.

Hi,

Thanks for getting back to me so quickly, the problem is that we don't know where the minimum is, so we don't know where to break as such....the error was that it could verify if f[b] >= f[b-0.0001].

We need the algorithm to break when f[b] is greater than the previous value of f[b] within the loop.  Also, we want the loop to print out just the two b and f[b] values (the one "greater than the previous", and the "previous").

Hope that makes sense.

Any ideas?

Thanks in advance.

Hi,

Sounds like it's a problem with your Java (I had a similar problem with another program that required java).

Java are aware of the problem - try the solutions that they have on their website, they worked for both of my laptops (but follow the instructions exactly) --> http://java.com/en/download/help/

Hope that helps!

Oh my days! You guys are geniuses! I had values for a and eps, but that one line for plot seems to be plotting the phase portrait brilliantly.  Thank you....