$$\bar{l}(\mathcal{P},\mathcal{L}) = \sum_{j=1}^n p_j l_j$$
I have just started studying this module and it describes the equation as the the average length of the code.
Can you please break down what each part of the equation means? I am a beginner and I need to try and understand how to breakdown this equation.
This means the average length $\overline l$ of a message given a set of symbols $\mathcal L$ and probability distribution $\mathcal P$ is the sum over all $n$ messages of the probability $p_j$ of message $j$ multiplied by its length $l_j$.