# Element modification

**URL:** <https://fenicsproject.discourse.group/t/element-modification/11679>\
**Category:** mesh\
**Created:** [July 6, 2023, 7:29pm UTC](https://fenicsproject.discourse.group/t/element-modification/11679 "2023-07-06T19:29:28Z")\
**Posts on this page:** 4\
**Page:** 1

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**Author:** ![mathew](https://avatars.discourse-cdn.com/v4/letter/m/5daacb/32.png) [@mathew](https://fenicsproject.discourse.group/u/mathew)\
**Post date:** [July 6, 2023, 7:29pm UTC](https://fenicsproject.discourse.group/t/element-modification/11679/1 "2023-07-06T19:29:28Z")

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Hi all,  
Suppose I have a quadrilateral mesh like this:

 ![initial](https://global.discourse-cdn.com/free1/uploads/fenicsproject1/original/2X/c/c638e2328c4faa9bb077596e8febee7abe2b0bca.png)

I want to modify third element from the left by reducing its height as shown below:

 ![proposed](https://global.discourse-cdn.com/free1/uploads/fenicsproject1/original/2X/7/7cd161b1f3128ff6fe50e2aa13d3dd30ff0b94f3.png)  
How can I do it in code.

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**Author:** ![dokken](https://yyz2.discourse-cdn.com/free1/user_avatar/fenicsproject.discourse.group/dokken/32/1560_2.png) [@dokken](https://fenicsproject.discourse.group/u/dokken)\
**Post date:** [July 6, 2023, 7:38pm UTC](https://fenicsproject.discourse.group/t/element-modification/11679/2 "2023-07-06T19:38:14Z")

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In legacy fenics you cannot.

In FEniCSx You can use DOLFINx\_mpc for this, as it requires you to mesh that shrunken quadrilateral individually, and you can glue the solutions together with «periodic» boundary conditions.

Ref: [GitHub - jorgensd/dolfinx\_mpc: Extension for dolfinx to handle multi-point constraints.](https://github.com/jorgensd/dolfinx_mpc)  
Disclaimer: Im the author of dolfinx\_mpc.

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<div class="post-metadata">

**Author:** ![mathew](https://avatars.discourse-cdn.com/v4/letter/m/5daacb/32.png) [@mathew](https://fenicsproject.discourse.group/u/mathew)\
**Post date:** [July 7, 2023, 4:35am UTC](https://fenicsproject.discourse.group/t/element-modification/11679/3 "2023-07-07T04:35:26Z")

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Thanks Sir.  
If I replace those two coordinates from the` mesh.coordinates()` and create mesh from array like [this](https://fenicsproject.discourse.group/t/create-mesh-in-fenicsx-from-point-and-element-array/9092/2).  
How can I replicate it in Fenics.

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<div class="post-metadata">

**Author:** ![dokken](https://yyz2.discourse-cdn.com/free1/user_avatar/fenicsproject.discourse.group/dokken/32/1560_2.png) [@dokken](https://fenicsproject.discourse.group/u/dokken)\
**Post date:** [July 7, 2023, 4:45am UTC](https://fenicsproject.discourse.group/t/element-modification/11679/4 "2023-07-07T04:45:11Z")

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Consider the demos of dolfinx\_mpc; [https://github.com/jorgensd/dolfinx\_mpc/blob/main/python/demos/demo\_periodic3d\_topological.py](https://github.com/jorgensd/dolfinx_mpc/blob/main/python/demos/demo_periodic3d_topological.py)  
[https://github.com/jorgensd/dolfinx\_mpc/blob/main/python/demos/demo\_elasticity\_disconnect\_2D.py](https://github.com/jorgensd/dolfinx_mpc/blob/main/python/demos/demo_elasticity_disconnect_2D.py)