Calculate rank of hash value and insert it into a CSV file in Ruby

Question

I have one hash

h1 = {"Cust1"=>500, "Cust4"=>400, "Cust2"=>100, "Cust3"=>100}

I want to insert this hash into a CSV file with the ranking of keys according to their value.

The sample output should look like this

ID,Sales,Rank Cust1,500,1 Cust4,400,2 Cust2,100,3 Cust3,100,3

I have to write the program in Ruby.

Answer 1

You can use each_with_index method of hash

arr = [['ID', 'Sales', 'Rank']]

h1.each_with_index do |(key, value), index|
  arr << [key, value, index + 1]
end

arr #[["ID", "Sales", "Rank"], ["Cust1", 500, 1], ["Cust4", 400, 2], ["Cust2", 100, 3], ["Cust3", 100, 4]]

Code for CSV

h1 = {"Cust1"=>500, "Cust4"=>400, "Cust2"=>100, "Cust3"=>100}
# You can skip following `sort_by` line if your hash is already ordered by desc value
h1 = h1.sort_by {|_k,v| v}.reverse.to_h
h2 = h1.group_by {|k,v| v }
require 'csv'
CSV.open("myfile.csv", "w") do |csv|
  csv << ['ID', 'Sales', 'Rank']
  h2.each_with_index do |(key, values), index|
    values.each do |value|
      csv << [value[0], key, index + 1]
    end
  end
end