How to group and count occurrences of values in Elixir's list
Join Elixir newsletter
Subscribe to receive Elixir news to your inbox every two weeks.
Expand your skills
Download free e-books, watch expert tech talks, and explore open-source projects. Everything you need to grow as a developer - completely free.
If you ever had to count occurrences of values in Elixir's list, this short post might be helpful for you!
Let's assume that the input contains a list of people names:
people = [
%{name: "John"},
%{name: "Tom"},
%{name: "John"},
%{name: "David"}
]Our goal here is to count occurrences of names so that in the end we'll get this summary:
%{"David" => 1, "John" => 2, "Tom" => 1}In Elixir, it's super easy! You can use Enum.frequencies_by/2 to achieve that in a simple one-liner:
iex > Enum.frequencies_by(people, & &1.name)
%{"David" => 1, "John" => 2, "Tom" => 1}Work with a team that keeps learning and building better software every day.
Related posts
Dive deeper into this topic with these related posts
You might also like
Discover more content from this category
The macro mechanism in Elixir is not only an interesting metaprogramming feature - in fact, it is at the language's very core. And the more awesome fact is that, using macros, you can override the algorithm of defining functions itself!
Nowadays, with an ever-growing number of web services, we tend to overload Web apps with external resources. As a result, it decreases page load speed and affects SEO score. There is a pretty easy solution for that.
Sooner or later you'll have to change the null constraint in one of your DB relations. How to do it easily in Ecto?