# Trying to just get the matrix for operations in an fespace

**URL:** https://community.freefem.org/t/trying-to-just-get-the-matrix-for-operations-in-an-fespace/2264
**Category:** General Discussion
**Created:** [February 6, 2023, 9:32am UTC](https://community.freefem.org/t/trying-to-just-get-the-matrix-for-operations-in-an-fespace/2264 "2023-02-06T09:32:29Z")
**Posts on this page:** 1
**Page:** 1

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### Author: ![marchywka](https://avatars.discourse-cdn.com/v4/letter/m/ee59a6/32.png) [@marchywka](https://community.freefem.org/u/marchywka)
#### Post date: [February 6, 2023, 9:32am UTC](https://community.freefem.org/t/trying-to-just-get-the-matrix-for-operations-in-an-fespace/2264/1 "2023-02-06T09:32:29Z")

</div>

from the documentation it looks like its possible to add customized finite element  
types but just as a learning exercise, and I even had a specific usage in mind, is it  
possible to dump the calculation of simple things like derivatives in an fespace?  
For example, something like this,

```auto
` 1 : 
    2 : mesh Th = square(10,10);
    3 : fespace Xh(Th,P0);
    4 : matrix A=dx(Xh) error operator ( <PP5v_fes> 
 List of choices 
	 ( <10LinearCombI6MDroit4C_F0E> : <10LinearCombI6MDroit4C_F0E> )
	 ( <St7complexIdE> : <St4pairIP6FEbaseISt7complexIdE6v_fesLEiE> )
	 ( <d> : <St4pairIP6FEbaseId6v_fesLEiE> )
	 ( <St7complexIdE> : <St4pairIP6FEbaseISt7complexIdE6v_fesSEiE> )
	 ( <d> : <St4pairIP6FEbaseId6v_fesSEiE> )
	 ( <St7complexIdE> : <St4pairIP6FEbaseISt7complexIdE6v_fes3EiE> )
	 ( <d> : <St4pairIP6FEbaseId6v_fes3EiE> )
	 ( <St7complexIdE> : <St4pairIP6FEbaseISt7complexIdE5v_fesEiE> )
	 ( <d> : <St4pairIP6FEbaseId5v_fesEiE> )
	 ( <10LinearCombI7MGauche4C_F0E> : <10LinearCombI7MGauche4C_F0E> )

```