Take the 2-minute tour ×
Mathematics Stack Exchange is a question and answer site for people studying math at any level and professionals in related fields. It's 100% free, no registration required.

I've encountered this symbol that looks like a capital $\mathbb{E}$ (with double vertical lines), which I am not familiar with, and I have no idea what to search for to find what it means, so apologies if it is something trivial.

The context in which it is written is as follows:

$R=\sum^\mathcal{T}_{t=1}\lambda^{t-1}\mathbb{E}[r^t]$

What does the $\mathbb{E}$ stand for?

Update Some more context:

$\mathcal{T}$ is the set of timeslots over which something is happening. $t\in\mathcal{T}$ (i.e. each timeslot). $\lambda$ is a discount factor raised to the timeslot its related to. $r^t$ is a reward collected at time $t$, and $R$ is supposedly calculating the total discounted reward over all timeslots in $\mathcal{T}$.

I haven't got much more information (trying to understand this thing myself).

share|improve this question
    
Please some more context. At least, what these $R,t,\mathcal T,\lambda,r$ are? Is there some probability around? –  Berci Feb 14 '13 at 15:07
    
I've seen $\mathbb{E}$ used to denote Euclidean Space, but not sure if that's what's meant here. –  amWhy Feb 14 '13 at 15:08
1  
It could also mean the Expected value if used in probability and statistics context –  Paresh Feb 14 '13 at 15:11

2 Answers 2

up vote 3 down vote accepted

The $\Bbb{E}$ means either Euclidean space, the expected value of a random variable, or a field in a tower of fields. This is from wikipedia. In your context it seems most likely to be the expected value of a random variable.

share|improve this answer
    
Thanks for pointing me to the right direction on wiki. Yes it seems that it is the expected value of a random variable. –  jbx Feb 14 '13 at 15:19

The font is the blackboard font. In the context you show, it is likely to be the expectation operator (integral) of probability.

share|improve this answer
    
Yes thanks a lot for your answer. It seems so. –  jbx Feb 14 '13 at 15:19

Your Answer

 
discard

By posting your answer, you agree to the privacy policy and terms of service.

Not the answer you're looking for? Browse other questions tagged or ask your own question.