# What does this Notation mean: N.“some cumulative distribution function”?

What does $N.\hat{N}_{fa}(S)$ mean, when $\hat{N}_{fa}(S)$ is a cumulative distribution function? $\hat{N}_{fa}(S) = \sum\limits_{s=0}^{S}\hat{p}_{fa}(s)$

The formula is from this paper (section 4.2): Logo Retrieval with A Contrario Visual Query Expansion

• A bit of context would be nice. (Where did you see this written?) – Willie Wong Feb 10 '11 at 12:32
• Sure, see my edit. – tauran Feb 10 '11 at 13:30

I'm pretty sure $N$ in the context means the size of the set $\Omega$, the total number of images. See beginning of section 3.1 of the linked paper. And in $N.\hat{N}_{fa}(S)$, the $.$ should just be multiplication. So the entire term should be interpreted as a distribution of the number of false alarms (total number times the cumulative distribution).