# Why ?Try to get unset x,y,

**URL:** <https://community.freefem.org/t/why-try-to-get-unset-x-y/1735>\
**Category:** General Discussion\
**Created:** [May 13, 2022, 2:55am UTC](https://community.freefem.org/t/why-try-to-get-unset-x-y/1735 "2022-05-13T02:55:55Z")\
**Posts on this page:** 2\
**Page:** 1

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**Author:** ![Qianrui](https://avatars.discourse-cdn.com/v4/letter/q/9fc348/32.png) [@Qianrui](https://community.freefem.org/u/Qianrui)\
**Post date:** [May 13, 2022, 2:55am UTC](https://community.freefem.org/t/why-try-to-get-unset-x-y/1735/1 "2022-05-13T02:55:55Z")

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Good morning. The code can run in 2D, but it can’t run in 3D. I found that the original line of code can’t run in 3D. The code is as follows

> if(psai0\>=1-k)  
> {  
> Eq1;  
> }  
> psai0=psai1;

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**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:** [May 16, 2022, 12:00pm UTC](https://community.freefem.org/t/why-try-to-get-unset-x-y/1735/2 "2022-05-16T12:00:25Z")

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psai0 is a finite element function, to get a value you need to set x,y or x,y,z.