Let’s suppose i want that some information, maybe electric field, maybe magnetic field or other field, be restricted only to a certain region of the world volume. How could i achieve this?

I have read a code that is like this:

```
if (20.003*mm >= sqrt(pow(Point[0]*mm,2)+pow(Point[1]*mm,2))) {
.... //where ... here would contain the information to be restricted only at the positions above.
}
```

So, is that the right way to restrict a information under some region of the space? In this case, a disk. What does it means Point[0] or Point[1]?

Could it be something like that?

```
if (20.003*mm >= sqrt(pow(x,2)+pow(y,2))) {
.... //where ... here would contain the information to be restricted only at the positions above.
}
```