Group Hash by Values in Ruby

Group Hash by values in ruby

You can group hash by its value:

h1 = {
  "admin_milestones"=>"1",
  "users_milestones"=>"0",
  "admin_goals"=>"1",
  "users_goals"=>"0", 
  "admin_tasks"=>"1", 
  "users_tasks"=>"0",
  "admin_messages"=>"1",
  "users_messages"=>"0",
  "admin_meetings"=>"1",
  "users_meetings"=>"0"
}

h2 = h1.group_by{|k,v| v}

It will produce a hash grouped by its values like this:

h2 = {"1"=>[["admin_milestones", "1"], ["admin_goals", "1"], ["admin_tasks", "1"], ["admin_messages", "1"], ["admin_meetings", "1"]], 
"0"=>[["users_milestones", "0"], ["users_goals", "0"], ["users_tasks", "0"], ["users_messages", "0"], ["users_meetings", "0"]]} 

Ruby hash group by value

I would do something like this:

student_marks.group_by { |k, v| v }.map { |k, v| [k, v.map(&:first)] }.to_h
#=> { 50 => ["Alex", "Matt"], 54 => ["Beth"]}

Ruby group hashes based on matching keys and store the value of non matching keys in an array

You can try grouping by key and value and then map the revenue values:

foos
  .group_by { |e| e.values_at(:key, :value) }
  .map do |(key, value), values|
    { key: key, value: value, revenue: values.map { |e| e[:revenue] } }
  end
# [{:key=>"Foo", :value=>1, :revenue=>[2, 4]}, {:key=>"Bar", :value=>2, :revenue=>[7]}, {:key=>"bar", :value=>2, :revenue=>[9]}, {:key=>"Zampa", :value=>4, :revenue=>[9]}]

i want to make a group Hash by keys and add values

I'd use the each_with_object method.
(key, value) here is a deconstruction of each key/value pair like 93=>1, hash is an intermediate object to store the result.

data.each_with_object({}) do |(key, value), hash|
  result_key = 
      case key
      when 10..19 then 1
      when 20..29 then 2
      when 90..99 then 9
      end
  next if result_key.nil?    
  hash[result_key] ||= 0
  hash[result_key] += value    
end

For the provided input I got {9=>2, 2=>7856, 1=>267}

UPD

A shorter solution suggested by Holger Just and Stefan in the comments below.

data.each_with_object(Hash.new(0)) do |(key, value), hash|
  hash[key / 10] += value
end

With Hash.new(0) the initial object will be a hash with the default value 0

> hash = Hash.new(0)
=> {}
> hash[1]
=> 0

Ruby group hashes by value of key

array.group_by {|x| x['type']}

or if you want the symbol key things you could even

array.group_by {|x| "type_#{x['type']}".to_sym}

I think this best expresses "So basically each array of hashes would be grouped by the value of its type key, and then returned as a hash with an array for each type", even if it leaves the :type key alone in the output hashes.

Ruby hashes group by multiple value

This seems to do what you want:

transformed_hash = initial_hash
  .group_by { |x| x['name'] }
  .map { |k, v| [k, v.group_by{ |x| x['folder'] }] }
  .to_h

Ruby Hash Group by two keys

You're grouping the result after the first group, but the hash content remains the same, you can use map to create a new hash only with the values you need:

report['count_by_state'].group_by { |count| count['policy_state'] }
                        .transform_values do |val|
                          val.to_h { |hash| hash.values_at('day', 'count') }
                        end
# {
# 2=>{"2021-02-23"=>48, "2021-02-25"=>1},
# 3=>{"2021-02-23"=>5,  "2021-02-25"=>4},
# 4=>{"2021-02-23"=>89, "2021-02-25"=>90}
# }

to_h is the short version of map { |...| [x, y] }.to_h, if your Ruby version doesn't support it yet, you can use that.

Group array of hashes by value and retain structure (hash) in Ruby

This should work:

hash.group_by { |k,v| v[:where] }.each { |_, v| v.map! { |array| { array[0] => array[1] } } }

Or with transform_values

hash.group_by { |k,v| v[:where] }.transform_values { |v| v.map { |array| {array[0] => array[1] } } }

https://ruby-doc.org/core-2.4.0/Hash.html#method-i-transform_values

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