# Denote a restricted function?

1. Dec 22, 2008

### Hootenanny

Staff Emeritus
How does one denote a restricted function?

For example, suppose I have a function $F : \mathbb{R}\to\mathbb{R}$, how would I denote a new function f, such that f is the restriction of F to the positive semi-axis? Up until this point I would have just said that f is the restriction of F to the positive semi-axis, but it occurs to me that there should be a more concise way of writing it.

2. Dec 22, 2008

### MathematicalPhysicist

Re: Restriction

f(x)=F(x) for only x positive real number, there's not a lot about it.

3. Dec 22, 2008

### Tac-Tics

Re: Restriction

$$f\vert_S$$ is the standard notation for the restriction of f to a subset S of f's domain.

4. Dec 22, 2008

### Hootenanny

Staff Emeritus
Re: Restriction

That's exactly was I was looking for Tac-Tics.

Thanks to you both.