# Variable boundary condition

**URL:** <https://community.freefem.org/t/variable-boundary-condition/1964>\
**Category:** General Discussion\
**Created:** [August 26, 2022, 6:29am UTC](https://community.freefem.org/t/variable-boundary-condition/1964 "2022-08-26T06:29:19Z")\
**Posts on this page:** 2\
**Page:** 1

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**Author:** ![sumantkr](https://yyz2.discourse-cdn.com/flex030/user_avatar/community.freefem.org/sumantkr/32/2681_2.png) [@sumantkr](https://community.freefem.org/u/sumantkr)\
**Post date:** [August 26, 2022, 6:29am UTC](https://community.freefem.org/t/variable-boundary-condition/1964/1 "2022-08-26T06:29:19Z")

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Hello,

I want to apply a functional base boundary condition to a section of the domain. Kindly comment for the correctness on the given code:

func f1= x\*y; //// boundary condition

…+ on( boundary, var = f1) ; // implementing bc on a domain

Or, help me if any relevant example is available.

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<div class="post-metadata">

**Author:** ![frederichecht](https://yyz2.discourse-cdn.com/flex030/user_avatar/community.freefem.org/frederichecht/32/15_2.png) [@frederichecht](https://community.freefem.org/u/frederichecht)\
**Post date:** [August 26, 2022, 9:58am UTC](https://community.freefem.org/t/variable-boundary-condition/1964/2 "2022-08-26T09:58:43Z")

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Dear sumantkr,

if f1 is a finite element function when you can change;

Vh f1=x\*y;

problem PB1( …+ on( boundary, var = f1) ; // implementing bc on a domain

PB1; // solve with x¨\*y

f1=x_y_y;  
PB1; // solve with x_y_y;