"Nasser M. Abbasi" wrote in message <firstname.lastname@example.org>... > On 5/24/2013 10:17 PM, Mateusz Gos wrote: > > Hi, > > > > I have a set of differential equations solved with ode45. > > At times it might be possible for the solver to find a valid time step > > (meeting the tolerance criteria), but for some of the variables in that > >time step to be physically not possible. So in other words such step is > >correct mathematically, but not physically. > > Of course I can check for these variables, but how do I make the solver > > discard a particular iteration and start a new one with different time > > step, regardless of what it has determined tolerance-wise? > > > > Thank you, > > Matt > > > > I do not know how you can make it discard the step, since it > allready made it. But may be you can stop ode45 at the point of > your choice and then restart it again using IC at that point > such that the new IC's is what you want to use. If so, you can > look at ode45 OutputFcn > > > http://www.mathworks.com/help/matlab/ref/odeset.html > > "The solver calls status = myfun(t,y,) after each integration step > on which output is requested. t contains points where output was generated > during the step, and y is the numerical solution at the points in t. " > > .... > > "myfun must return a status output value of 0 or 1. If status = 1, > the solver halts integration. You can use this mechanism, for > instance, to implement a Stop button." > > I've used OutputFcn for display the solution as ode45 was running > for another reason, but it is possible to use it to check for specific > conditions and halt ode45. Then restart again, since you know the > solution at that moment. > > --Nasser
Yes, I already use the output function anyway. I admit it is not the answer I was hoping for, but thanks for the idea.