Rails Ruby hash array, keyed to middle value

Question

I have an activerecord method that finds all events in a week   myevents.map { |x| x.start_date.day => [x.title]} (start_date is a date and time field, name is a string) which gives me an array of hashes;

    [{11=>["40"]}, {11=>["0"]}, {11=>["0"]}, {11=>[""]}, 
     {11=>["0"]}, {11=>["0"]}, {11=>["33"]}, {12=>["9"]}, 
     {11=>["34"]}, {11=>["29"]}, {11=>["8"]}, {11=>["31"]}, 
     {11=>["40"]}, {11=>["34"]}] 

I want to map values ​​to get an array that looks like this:

[ {11=>[ average of values that occur on the 11th]}, 
  {12=>[average of values that occur on the 12th]} ]

but I'm not quite sure how to get this.

Answer 1

I would use group_by, injectand map.

ar = [  
        {11=>["40"]}, {11=>["0"]}, {11=>["0"]}, {11=>[""]},
        {11=>["0"]}, {11=>["0"]}, {11=>["33"]}, {12=>["9"]},
        {11=>["34"]}, {11=>["29"]}, {11=>["8"]}, {11=>["31"]}, 
        {11=>["40"]}, {11=>["34"]}
     ]

# first grouping the inner hash keys like on 11,12,etc. In each iteration, 
# {11=>["40"]}, {11=>["0"]} are being passed to the block of `group_by`. Now
# `h.keys.first` gives 11 from `{11=>["40"]}` and 11 from `{11=>["0"]}` likewise.
ary = ar.group_by { |h| h.keys.first }.map do |k,v|
  { k => v.map { |h| h[k][0].to_i }.inject(:+) / v.size } 
end

ary # => [{11=>19}, {12=>9}]

Answer 2

Another approach: -

array = [  
        {11=>["40"]}, {11=>["0"]}, {11=>["0"]}, {11=>[""]},
        {11=>["0"]}, {11=>["0"]}, {11=>["33"]}, {12=>["9"]},
        {11=>["34"]}, {11=>["29"]}, {11=>["8"]}, {11=>["31"]}, 
        {11=>["40"]}, {11=>["34"]}
     ]

    array.each_with_object({}) { |hObj, newHash| hObj.each { |k,v| 
         (newHash[k] ||= []) << v.first.to_i } }.collect{|k,v| 
         {k => (v.inject(:+))/v.size}}

=> [{11=>19}, {12=>9}]