# Defining by parts properties
**URL:** https://community.freefem.org/t/defining-by-parts-properties/1446
**Category:** General Discussion
**Created:** [January 18, 2022, 4:50pm UTC](https://community.freefem.org/t/defining-by-parts-properties/1446 "2022-01-18T16:50:07Z")
**Posts on this page:** 4
**Page:** 1
### Author:  [@RaMattoso](https://community.freefem.org/u/RaMattoso)
#### Post date: [January 18, 2022, 4:50pm UTC](https://community.freefem.org/t/defining-by-parts-properties/1446/1 "2022-01-18T16:50:07Z")
Hello fellows!
I need to define different properties values for three or more regions in my domain.
Following the FreeFem documentation, I was able to build the mesh in a way that this regions are known.
Searching in this community I found how to do that. But, only the code for two differents properties works. When I try the code for three, the result is odd numbers (not necessary related to the ones I gave).
Let’s to the code
Building the mesh
```auto
int n=20;
real x0 = 0.0, x1 = 0.5, y0 = 0.0, y1 = 0.5;
real r = 0.15, cx = x1/2, cy = y1/2;
real rd = r/5;
border Q01(t=0, 1){x=x1*t; y=y0; label=1;}
border Q03(t=0, 1){x=x1-x1*t; y=y1; label=3;}
border Q04(t=0, 1){x=x0; y=y1-y1*t; label=4;}
border Q02(t=0, 1){x=x1; y=y1*t; label=2;}
border C01(t=0, 2*pi){x=cx+r*cos(t); y=cy+r*sin(t); label=5;}
border C02(t=0, 2*pi){x=cx+(rd)*cos(t); y=cy+(rd)*sin(t); label=6;}
Th0 = buildmesh (Q01(n) + Q02(n) + Q03(n) + Q04(n) + C01(-n));
Th1 = buildmesh (C01(n) + C02(-n));
Th2 = buildmesh (C02(n));
Th = buildmesh (Q01(n) + Q02(n) + Q03(n) + Q04(n) + C01(n) + C02(n));
```
Defining by parts property (this code works just fine, but it is only for two regions)
```auto
real reg1 = Th(0,0).region;
real reg2 = Th(0.35,0.35).region;
real reg3 = Th(0.25,0.25).region;
vk[0] = 1.0e-4; vk[1] = 0.12; vk[2] = 0.5;
fespace Ph(Th, P0);
Ph k = (region == reg1 ? vk[0] : vk[1]);
```
The code for three regions is the below (which is giving some strange result)
```auto
real reg1 = Th(0,0).region;
real reg2 = Th(0.35,0.35).region;
real reg3 = Th(0.25,0.25).region;
vk[0] = 1.0e-4; vk[1] = 0.12; vk[2] = 0.5;
fespace Ph(Th, P0);
Ph k = vk[0]*(region==reg1) + vk[1]*(region==reg2) + vk[2]*(region=reg3);
```
Can someone give me a help?
Thanks in advance!
---
### Author:  [@gero](https://community.freefem.org/u/gero)
#### Post date: [January 18, 2022, 8:58pm UTC](https://community.freefem.org/t/defining-by-parts-properties/1446/2 "2022-01-18T20:58:17Z")
For reg3 you use assignment (=) instead of comparison (==).
Although it doesn’t seem to cause a problem I would expect region numbers to be int rather than real.
---
### Author:  [@marcodeba](https://community.freefem.org/u/marcodeba)
#### Post date: [January 18, 2022, 8:59pm UTC](https://community.freefem.org/t/defining-by-parts-properties/1446/3 "2022-01-18T20:59:57Z")
Good evening!
There is only a little mistake within your script. Indeed in the last line you shared you wrote:
… (region=reg3), but of course you are required to use a proper logical operator which is in this case the == sign! So your last line should become something like:
```auto
Ph k = vk[0]*(region == reg1) + vk[1]*(region == reg2) + vk[2]*(region == reg3);
```
In such a way if you access your property in the region you defined you find the correct definition:
```auto
cout<<"k(reg1) = "<
### Author:  [@RaMattoso](https://community.freefem.org/u/RaMattoso)
#### Post date: [January 18, 2022, 9:39pm UTC](https://community.freefem.org/t/defining-by-parts-properties/1446/4 "2022-01-18T21:39:51Z")
Thank you so much @gero and @marcodeba !
I’m so embarrassed rn.
Since yesterday I haven’t be able to find the error in this code.
And it was dancing in front of me.
Thanks for the nice response.