Merging 3 Array/Hashes Into 1 and Preserve The Values

rubyonrails-talk
1

I'm currently building a mini stat page and tracking some users stats that I would like to combine into a large table for an overview. I currently have the following...

@new_users = [{"May Sat 03"=>5}, {"May Fri 02"=>1}, {"May Thu 01"=>4}] @new_entries = [{"May Sat 03"=>2}, {"May Fri 02"=>3}, {"May Thu 01"=>4}] @new_winners = [{"May Sat 03"=>3}, {"May Fri 02"=>4}, {"May Thu 01"=>4}]

I would like to generate one master array that I can iterate using a table. My thinking is I would want to have one master array that looks like this.

@master_list = [ {"May Sat 03"=> [5,2,3]}, {"May Sat 02"=> [1,3,4]}, {"May Sat 01"=> [4,4,4]} ]

or should it look might look like this

@master_list = [{"May Sat 03"=> ["new_users"=>"5","new_entries"=>"2","new_winners"=>"3"]},             {"May Sat 03"=> ["new_users"=>"5","new_entries"=>"2","new_winners"=>"3"]},             {"May Sat 03"=> ["new_users"=>"5","new_entries"=>"2","new_winners"=>"3"]}            ]

I would think this first option seems the easiest to produce?

Is there a way in Ruby or in Rails to tell each array to find the exact same index/key (which are the dates) and merge it's values? I have been playing around with Array.find_all and Array.inject but nothing seems to be clicking on how I would generate the final @master_list

2

After some researching online I found 1/2 a solution. (The example code was found on Hash#collate - Ruby - Ruby-Forum).

What you could do is this...

@master_list = @new_users.update(@new_entries) {|key, *values| values }

# Returns # {"May Sat 03"=>[5, 2], "May Fri 02"=>[1, 3], "May Thu 01"=>[4]}

Only issue is I can't merge the third array(@new_winners) into @master_list.

3

Hi --

I'm currently building a mini stat page and tracking some users stats that I would like to combine into a large table for an overview. I currently have the following...

@new_users = [{"May Sat 03"=>5}, {"May Fri 02"=>1}, {"May Thu 01"=>4}] @new_entries = [{"May Sat 03"=>2}, {"May Fri 02"=>3}, {"May Thu 01"=>4}] @new_winners = [{"May Sat 03"=>3}, {"May Fri 02"=>4}, {"May Thu 01"=>4}]

I would like to generate one master array that I can iterate using a table. My thinking is I would want to have one master array that looks like this.

@master_list = [ {"May Sat 03"=> [5,2,3]}, {"May Sat 02"=> [1,3,4]}, {"May Sat 01"=> [4,4,4]} ]

or should it look might look like this

@master_list = [{"May Sat 03"=> ["new_users"=>"5","new_entries"=>"2","new_winners"=>"3"]},            {"May Sat 03"=> ["new_users"=>"5","new_entries"=>"2","new_winners"=>"3"]},            {"May Sat 03"=> ["new_users"=>"5","new_entries"=>"2","new_winners"=>"3"]}           ]

I would think this first option seems the easiest to produce?

Is there a way in Ruby or in Rails to tell each array to find the exact same index/key (which are the dates) and merge it's values? I have been playing around with Array.find_all and Array.inject but nothing seems to be clicking on how I would generate the final @master_list

Here's one way:

arrays = [@new_users, @new_entries, @new_winners] master_list = arrays.transpose.map do |array|    hash = Hash.new {|h,k| h[k] = }      array.each do |stat|        stat.each do |date,n|          hash[date] << n        end      end    hash end

The transpose operation gets all of the ones with matching dates together, which then makes it easier to go through them and pluck out the values. The Hash.new formula gives you a hash whose default behavior for an unknown key is to create the key and initialize it to an empty array.

David

4

I have been working on this and soon realized that I should have made my keys using a :symbol instead of the actual data. So I have started from the beginning and modified some details

# My Array of data @new_users = [{:date=>"May Sat 10", :results=>6}, {:date=>"May Fri 09", :results=>1}, {:date=>"May Mon 05", :results=>0}] @new_entries = [{:date=>"May Sat 10", :results=>2}, {:date=>"May Fri 09", :results=>1}, {:date=>"May Mon 05", :results=>1}] @new_winners = [{:date=>"May Sat 10", :results=>3}, {:date=>"May Fri 09", :results=>1}, {:date=>"May Mon 05", :results=>2}]

# The way of merging them into a master_list This is where I'm currently stuck and trying out stuff. I'm playing around with David's code but I'm not getting the result I need.

# My end result should look like this master_list = [{:date=> "May Sat 10", :results=>[6,2,3]},{:date=> "May Fri 09", :results=>[1,1,1]},{:date=> "May Mon 05", :results=>[0,1,2]}]

# My View master_list.sort_by { |line_item| line_item[:date] }.each do | line_item|    puts "#{line_item[:date]}, #{line_item[:results][0]}, #{line_item[:results][1]}, #{line_item[:results][2]}" end

If you David or anyone else on the forum can help out again, that would be much appreciated

5

Seems to me you are putting redundant information into your data. You know the first half is a date and the second half is a result. Make a hash with the date as a symbol and the result as a value.

@new_users = {:May_Sat_10=>6 , :May_Fri_09=>1, :May_Mon_05=>0} @new_entries = {:May_Sat_10=>2, :May_Fri_09=>1, :May_Mon_05=>1} @new_winners = {:May_Sat_10=>3, :May_Fri_09=>1, :May_Mon_05=>2}

  def add_to_hash(my_hash, combined_hash)     my_hash.inject(combined_hash) do |new_hash, (key, value)|       (new_hash[key] ||= ) << value       new_hash     end   end

cool_hash = {} add_to_hash(@new_users, cool_hash) add_to_hash(@new_entries , cool_hash) add_to_hash(@new_winners , cool_hash)

puts "cool Hash" p cool_hash

6

Thanks for your solution. I tried it but I'm getting errors. The errors are getting generated in the def add_to_hash method your proposing.

I'm just curious why wouldn't my current proposal of using symbols be correct and not redundant? So far I have read that "...symbols are useful whenever you're going to be re-using a word over and over to represent something...". Am I misusing the way a symbol should be used in my proposal?

7

Disregard the error issue. I just found that I had some odd invisible characters in my code. I guess it's not a good idea to copy and paste directly. So your solution works fine.

I still would like to understand the issue around my proposed way of using symbols.

8

Symbols are great, and there is nothing wrong with what your are doing, I am just saying that you repeat :date and :result for every record. You could just have a hash with the date as the hash key (:May_Sat_10) and the result as a hash value rather than a two sets, a key (:date) with a value of a date and second key(:result) with a numeric value. Having :date and :result in every record isn't really necessary, but you might have a need that I don't know about. It's the same information, just that one format is less verbose.

@new_users = [{:date=>"May Sat 10", :results=>6}, {:date=>"May Fri 09", :results=>1}, {:date=>"May Mon 05", :results=>0}] vs @new_users = {:May_Sat_10=>6 , :May_Fri_09=>1, :May_Mon_05=>0}

Ruby onward and good luck.

9

I like your example the only issue for me is I need to output everything out into a table. The idea of having.. May_Sat_10 May_Fri_09

is not easy on the eyes. I also found that its difficult to actual sort with your solution.

Maybe it's not as pretty as it needs to be, but I need to convert those 3 arrays into one using this type of formatting (see example)

@new_users = [{:date=>"May Sat 10", :results=>6}, {:date=>"May Fri 09", :results=>1}] @new_entries = [{:date=>"May Sat 10", :results=>2}, {:date=>"May Fri 09", :results=>3}] @new_winners = [{:date=>"May Sat 10", :results=>3}, {:date=>"May Fri 09", :results=>4}]

that way, when I output this to a table I'll be able to use this and sort it very easily

# output master_list.sort_by { |line_item| line_item[:date] }.each do | line_item|    puts "#{line_item[:date]}, #{line_item[:results][0]}, #{line_item[:results][1]}, #{line_item[:results][2]}" end

Thanks for your input so far