# Using callback functions when solving pde's with MethodOfLines

**URL:** <https://discourse.julialang.org/t/using-callback-functions-when-solving-pdes-with-methodoflines/101379>\
**Category:** General Usage\
**Tags:** diffeqcallbacks\
**Created:** [July 9, 2023, 7:47am UTC](https://discourse.julialang.org/t/using-callback-functions-when-solving-pdes-with-methodoflines/101379 "2023-07-09T07:47:48Z")\
**Posts on this page:** 2\
**Page:** 1

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**Author:** ![mkretzschmar](https://avatars.discourse-cdn.com/v4/letter/m/ba8739/32.png) [@mkretzschmar](https://discourse.julialang.org/u/mkretzschmar)\
**Post date:** [July 9, 2023, 7:47am UTC](https://discourse.julialang.org/t/using-callback-functions-when-solving-pdes-with-methodoflines/101379/1 "2023-07-09T07:47:48Z")

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I am using the MethodOfLines package for solving a system of first order pde’s. Now I want to introduce callback functions to handle discrete events. It is unclear to me how to call the integrator, because the pde system has been changed by discretization into an ODE system. How are the fields of the ODE system obtained by discretization called?

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**Author:** ![ChrisRackauckas](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/chrisrackauckas/32/77_2.png) [@ChrisRackauckas](https://discourse.julialang.org/u/ChrisRackauckas)\
**Post date:** [July 9, 2023, 10:38am UTC](https://discourse.julialang.org/t/using-callback-functions-when-solving-pdes-with-methodoflines/101379/2 "2023-07-09T10:38:22Z")

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ODESystem had this capability, but I’m not sure PDRSystem does yet. Open an issue.