Time crossing poincaresos ?

[gacarita]

Hi,

As I understand the poincaresos function does not return timecrossings events. Could this be a new feature ?

[Datseris]

Hi,

this is trivial to do, as the necessary information is already accessible in the source code. In fact, the function first calculates the crossing times and then simply returns the integrator state at these times.

https://github.com/JuliaDynamics/ChaosTools.jl/blob/master/src/orbitdiagrams/poincare.jl#L168-L169

But one has to be very careful for directly supporting this in DynamicalSystems.jl. poincaremap! is a deeply rooted function. It is used in several places of the entire library. Changing its return signature would be really breaking. So your options are: either just copy/paste the code and do the necessary 3 lines of code modification so that the code returns what you need, or, open a pr that creates a new function. Return the crossing times in the existing functions is not possible for compatibility reasons.

[awage]

Hello,

here is another solution, you can define a pmap object to track the orbit step by step:

ds = Systems.rikitake([0.,0.,0.], μ = 0.47, α = 1.0)
pmap = poincaremap(ds, (3,0.), Tmax=200.)
next_state_on_psos = step!(pmap)
tcross = pmap.integ.t  # here is your crossing time

[Datseris]

Great, so we only need to document this in poincaremap function! No reason to add extra functions or so.

[gacarita]

sounds good thanks ! :)

[Datseris]

Issue stays open until this is documented.

[gacarita]

Ok. I'm sorry for closing the topic, I didn't know that. I appreciate the help.

[Datseris]

Actually, this is not correct:

tcross = pmap.integ.t  # here is your crossing time

this is not the time crossing the section unfoirtunately, but after the cross. To get the time crossing the section you'd need to call tcross = current_time(pmap). This is implemented, and will be released after #237 is merged.