Get the count of distinct values from a Sequence in F#

Question

I have a sequence of Country names in F#. I want to get how many of each distinct country entries do I have in the sequence.

The countBy examples in Microsoft docs and MSDN use if and else to get the Keys, but since I have ~240 distinct entries, I guess that I don't need to make an elif sentence for each entry, right?

So, is there an option to use another sequence to get the keys for the countBy?

#load "packages/FsLab/FsLab.fsx"
open FSharp.Data
open System

type City = JsonProvider<"city.list.json",SampleIsList=true>

let cities = City.GetSamples()

let Countries = seq { for city in cities do yield city.Country.ToString() } |> Seq.sort

let DistinctCountries = Countries |> Seq.distinct

//Something like this
let Count = Seq.countBy DistinctCountries Countries

Anyone interested in my city.list.json

Update

My input sequence is something like this (with a lot more of entries) with each code repeated as many cities for that country are in the original list:

{ "AR","AR","AR","MX","MX" }

As a result I expect:

{("AR", 3),("MX", 2),...}

Answer 1

Countries |> Seq.countBy id

id is the identity function fun x -> x. Use this because the "key" here is the sequence item itself.