# About mesh region and label

**URL:** <https://community.freefem.org/t/about-mesh-region-and-label/2840>\
**Category:** General Discussion\
**Created:** [December 20, 2023, 10:00am UTC](https://community.freefem.org/t/about-mesh-region-and-label/2840 "2023-12-20T10:00:59Z")\
**Posts on this page:** 4\
**Page:** 1

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**Author:** ![qingYang](https://avatars.discourse-cdn.com/v4/letter/q/9f8e36/32.png) [@qingYang](https://community.freefem.org/u/qingYang)\
**Post date:** [December 20, 2023, 10:00am UTC](https://community.freefem.org/t/about-mesh-region-and-label/2840/1 "2023-12-20T10:00:59Z")

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Hello everyone, I extracted a certain face from the externally imported mesh as a 2D mesh (Th), but after extraction, all regions and labels in Th are 0 (as shown in the figure). I want to know how to assign regions and labels to each part, and ultimately, what I want to do is use Th to build layer grids.

 ![12.20](https://canada1.discourse-cdn.com/flex030/uploads/freefem/original/2X/5/56826c6f14c326570b9e1c3637d235a0fcd6f449.png)

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**Author:** ![qingYang](https://avatars.discourse-cdn.com/v4/letter/q/9f8e36/32.png) [@qingYang](https://community.freefem.org/u/qingYang)\
**Post date:** [December 21, 2023, 7:53am UTC](https://community.freefem.org/t/about-mesh-region-and-label/2840/2 "2023-12-21T07:53:56Z")

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Is anyone willing to give me some advice? thank you.

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**Author:** ![denis.crete](https://avatars.discourse-cdn.com/v4/letter/d/9d8465/32.png) [@denis.crete](https://community.freefem.org/u/denis.crete)\
**Post date:** [October 9, 2025, 1:40pm UTC](https://community.freefem.org/t/about-mesh-region-and-label/2840/3 "2025-10-09T13:40:13Z")

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Dear qingYang,  
I don’t know why this mail reached me only today, but it seems that the question dates back in 2023… I hope you’ve found a solution since then.  
As I had also some troubles with the numbering of the regions and borders, it is still of interest to me.

Did you try to use the “change” command ? e.g. p62 “Sh = change(Sh,flabel =…)” , or detailed presentation Chapter 3 p134 of Manual 4.13 …  
HTH  
Denis

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**Author:** ![qingYang](https://avatars.discourse-cdn.com/v4/letter/q/9f8e36/32.png) [@qingYang](https://community.freefem.org/u/qingYang)\
**Post date:** [October 10, 2025, 12:32am UTC](https://community.freefem.org/t/about-mesh-region-and-label/2840/4 "2025-10-10T00:32:18Z")

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This is truly unbelievable.  
Thank you for your attention and reply. This was a problem I encountered when I first started, and it has now been resolved.  
Wishing you a happy life, Denis