Iverson Bracket / Conditional Sum of a string I'm trying to turn calculations that I've been using on a data set into mathematic notation to write it down in a research paper.
One of my calculations creates a factor that determines how often a certain value (in this case the geographic location of $r$), appears in a string $s$. 
As a definition I wrote:
$\Gamma$ is defined for a release $r$ as the number of its occurrences in the sequence $s$ divided by count of all its elements $n$. After readingh trhough various articles I based my notation to cases where people used Iverson brackets (Mathematical notation for a conditional sum) and came up with following:
\begin{equation}
\Gamma(r_{iso}) = \frac{\sum_{i=1}^{n} \Big[ s_{i} = r_{iso}\Big]}{n}
\end{equation}
\begin{align*}
\text{where}\\~r_{iso} &= \text{release origin of r} \\ 
  s_{i} &= \text{sequence of all accounted geographic locations}
\end{align*}
Reading this, would a math ninja scream out of agony or does this seem about right? Are there other / better ways of expressing this definition?
Thanks for your help!

It wouldn’t bother me, though if I took this approach I’d probably write it
$$\Gamma(r_{iso})=\frac1n\sum_{i=1}^n[s_i=r_{iso}]$$
instead. Unfortunately, quite a few people are still unfamiliar with Iverson brackets, so it would probably be better to use a more familiar alternative. Perhaps the simplest is
$$\Gamma(r_{iso})=\frac1n\big|\{i:s_i=r_{iso}\}\big|$$
or
$$\Gamma(r_{iso})=\frac{\big|\{i:s_i=r_{iso}\}\big|}n\;,$$
depending on person preference.
