# Regions permittivity
**URL:** https://community.freefem.org/t/regions-permittivity/830
**Category:** General Discussion
**Created:** [March 3, 2021, 6:25pm UTC](https://community.freefem.org/t/regions-permittivity/830 "2021-03-03T18:25:59Z")
**Posts on this page:** 9
**Page:** 1
### Author:  [@niaa](https://community.freefem.org/u/niaa)
#### Post date: [March 3, 2021, 6:25pm UTC](https://community.freefem.org/t/regions-permittivity/830/1 "2021-03-03T18:25:59Z")
Hello colleagues,
I have a domain with two different regions ( region 1 and region 2). I need to define a function for permittivity so that in region 1 it considers the permittivity of air but in the region 2 another permittivity.
Does this command is proper to get this goal:
real ep = 12;
real er= 1;
func erregion = (region == 1 ? er : ep);
thanks for your help.
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### Author:  [@mrbenson](https://community.freefem.org/u/mrbenson)
#### Post date: [March 4, 2021, 7:17pm UTC](https://community.freefem.org/t/regions-permittivity/830/2 "2021-03-04T19:17:32Z")
func erregion = er\*(region == 1) + ep\*(region==2);
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### Author:  [@niaa](https://community.freefem.org/u/niaa)
#### Post date: [March 4, 2021, 8:04pm UTC](https://community.freefem.org/t/regions-permittivity/830/3 "2021-03-04T20:04:36Z")
thanks, but I have tried this command before, but it doesn’t give me the answer…
the one that I suggested is wrong?
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### Author:  [@prj](https://community.freefem.org/u/prj)
#### Post date: [March 6, 2021, 11:23am UTC](https://community.freefem.org/t/regions-permittivity/830/4 "2021-03-06T11:23:14Z")
Use a piecewise constant function.
```auto
fespace Ph(Th, P0);
Ph erregion = (region == 1 ? er : ep);
```
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### Author:  [@niaa](https://community.freefem.org/u/niaa)
#### Post date: [March 7, 2021, 6:12pm UTC](https://community.freefem.org/t/regions-permittivity/830/5 "2021-03-07T18:12:03Z")
I get error via this command;
can you please help me in defining proper command for permittivity of a domain with 2 regions ? Its like considering a dielectric object in free space.
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### Author:  [@prj](https://community.freefem.org/u/prj)
#### Post date: [March 7, 2021, 6:16pm UTC](https://community.freefem.org/t/regions-permittivity/830/6 "2021-03-07T18:16:27Z")
I’ve tried my previous script, it works as expected, assuming you have properly defined the mesh `Th` of course.
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### Author:  [@niaa](https://community.freefem.org/u/niaa)
#### Post date: [March 7, 2021, 6:36pm UTC](https://community.freefem.org/t/regions-permittivity/830/7 "2021-03-07T18:36:17Z")
Thanks for your quick response. I changed sth and it works now.
The problem by defining as func erregion = (region == 1 ? er : ep); was that when I changed it to " func erregion = (region == 2 ? ep : er); " , the solotion became different. I guess it was just considering the first permittivity not other one.
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### Author:  [@niaa](https://community.freefem.org/u/niaa)
#### Post date: [March 7, 2021, 6:51pm UTC](https://community.freefem.org/t/regions-permittivity/830/8 "2021-03-07T18:51:03Z")
May you tell me please what was wrong with difining as func ?
thanks alot.
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### Author:  [@frederichecht](https://community.freefem.org/u/frederichecht)
#### Post date: [March 10, 2021, 3:46pm UTC](https://community.freefem.org/t/regions-permittivity/830/9 "2021-03-10T15:46:29Z")
remark, in this examples you can do is you have only 2 regions 1 and 2.
real[int] ee=[0.,1.,12.] ;
func erregion = ee[region];