Adding Hashes from an array

Question

I am trying to create an array/hash from an array of multiple hashes with same keys and an average of values. My array:

[{:amount=>897500, :gross_amount=>897500, :tax=>147500, :hotel_fees=>0, :base_fare=>750000, :currency=>"INR"}, {:amount=>1006500, :gross_amount=>1006500, :tax=>156500, :hotel_fees=>0, :base_fare=>850000, :currency=>"INR"}]

Now I want to return something like this:

{:amount=>952000, :gross_amount=>952000, :tax=>152000, :hotel_fees=>0, :base_fare=>800000, :currency=>"INR"}

where values are the average of values from each hash with same key.

Is there a simple way to do this. I have tried using merge but currency becomes 0 with it.

My attempt:

p[0].merge(p[1]){|k,v1,v2| (v1+v2)/2 unless v1 && v2 == "INR"}

Edit:

Actually my problem didn't end here, so after getting the average I needed to insert the values inside another hash. So I used something like this:

        price_array = offer_values.map do |v| 
          v.inject do |k, v| 
            k.merge!(price: k[:price].merge(v[:price]){|_, a, b| [a, b].flatten })
          end
        end
        price_array.map do |o|
          o[:price] = {}.tap{ |h| o[:price].each {|k, list| h[k] = list.all?{|e| [Fixnum, NilClass].include? e.class} ? list.map(&:to_i).sum/list.size : list.compact.first ; h  } }
        end

Where offer_array is the one with my orginal/first array in separate hashes. This I have tried for with 2 and 3 hashes and it is working.

If you guys have any suggestion on improving the code, It am open.

"I have tried using merge" – could you show your attempt? — Stefan
– Stefan, Commented Jun 13, 2017 at 15:53
Merge returns this {:amount=>952000, :gross_amount=>952000, :tax=>152000, :hotel_fees=>0, :base_fare=>800000, :currency=>nil} — Ravi
– Ravi, Commented Jun 13, 2017 at 15:54
My attempt: p[0].merge(p[1]){|k,v1,v2| (v1+v2)/2 unless v1 && v2 == "INR"} — Ravi
– Ravi, Commented Jun 13, 2017 at 15:56
It's a bit hard to read code in comments, you you edit your question instead? — Stefan
– Stefan, Commented Jun 13, 2017 at 15:56

Ramon Marques · Accepted Answer · 2017-06-13 16:01:25Z

3

Irb

2.2.3 :011 > b = {test1: 30, test2: 40}
 => {:test1=>30, :test2=>40} 
2.2.3 :012 > a = {test1: 20, test2: 60}
 => {:test1=>20, :test2=>60} 
2.2.3 :013 > c = a.merge(b){|key, oldval, newval| (newval + oldval)/2}
 => {:test1=>25, :test2=>50}

answered Jun 13, 2017 at 16:01

Ramon Marques

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1 Comment

Ravi Over a year ago

ohh I thought it was some thing else.

Ramon Marques · Accepted Answer · 2017-06-13 18:11:33Z

2

The accepted answer will not work for more than 2 hashes, since merge works only 2 by 2 and you are calculating average here.

(((3 + 2) / 2) + 2.5) / 2 is different from (3 + 2 + 2.5) / 3

So I wrote a piece of code that could do what you want for whatever size of array you have

  def self.merge_all_and_average(array)
    new_hash = {}
    unless array.empty?
      array[0].keys.each do |key|
        if array[0][key].class == Fixnum
          total = array.map { |i| i[key] }.inject(0) { |sum, x| sum + x }
          new_hash = new_hash.merge(key => total / array.size)
        else
          new_hash = new_hash.merge(key => array[0][key])
        end
      end
    end
    new_hash
  end

edited Jun 13, 2017 at 18:11

answered Jun 13, 2017 at 17:00

Ramon Marques

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1 Comment

Ravi Over a year ago

I know it won't work for more than two hash. I just wanted an idea on how I could handle it. I was on the right path but couldn't get correct answer. My problem never was totally different and various other things were involved. This was just a part of it where I was getting confused. The solution I have used is somewhat similar to yours. Check my edit.

Eric Duminil · Accepted Answer · 2017-06-13 21:11:02Z

2

This should work with any number of hashes:

data = [
  { amount: 897_500, gross_amount: 897_500, tax: 147_500, hotel_fees: 0, base_fare: 750_000, currency: 'INR' },
  { amount: 1_006_500, gross_amount: 1_006_500, tax: 156_500, hotel_fees: 0, base_fare: 850_000, currency: 'INR' },
  { amount: 1_006_500, gross_amount: 1_006_500, tax: 156_500, hotel_fees: 0, base_fare: 850_000, currency: 'INR' }
]

transposed_hashes = data.each_with_object(Hash.new{|h, k| h[k] = []}) do |h, mem|
  h.each do |k, v|
    mem[k] << v
  end
end
# {:amount=>[897500, 1006500, 1006500], :gross_amount=>[897500, 1006500, 1006500], :tax=>[147500, 156500, 156500], :hotel_fees=>[0, 0, 0], :base_fare=>[750000, 850000, 850000], :currency=>["INR", "INR", "INR"]}

average_hash = transposed_hashes.map do |k, v|
  new_value = if v[0].is_a? Integer
                v.sum.to_f / v.size
              else
                v[0]
              end
  [k, new_value]
end.to_h

puts average_hash
# {:amount=>970166.6666666666, :gross_amount=>970166.6666666666, :tax=>153500.0, :hotel_fees=>0.0, :base_fare=>816666.6666666666, :currency=>"INR"}

answered Jun 13, 2017 at 21:11

Eric Duminil

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1 Comment

Ravi Over a year ago

I am doing something similar as well but this method increases my complexity of the code.

Sebastián Palma · Accepted Answer · 2017-06-28 14:06:38Z

1

For two hashes in array you could use inject and merge checking if the value for the both currency keys are Fixnum class, if not, then take the value of currency "INR" in the first hash and use it:

array = [
  {:amount=>897500,  :gross_amount=>897500,  :tax=>147500, :hotel_fees=>0, :base_fare=>750000, :currency=>"INR"}, 
  {:amount=>1006500, :gross_amount=>1006500, :tax=>156500, :hotel_fees=>0, :base_fare=>850000, :currency=>"INR"}
]

p array.inject{|k,v| k.merge(v){|_,a,b| [a,b].all?{|e| e.is_a?(Fixnum)} ? (a+b)/2 : b}}
# => {:amount=>952000, :gross_amount=>952000, :tax=>152000, :hotel_fees=>0, :base_fare=>800000, :currency=>"INR"}

For two or more hashes in an array you could try with:

main_array = [
  {:amount=>897500,  :gross_amount=>897500,  :tax=>147500, :hotel_fees=>0, :base_fare=>750000, :currency=>"INR"}, 
  {:amount=>1006500, :gross_amount=>1006500, :tax=>156500, :hotel_fees=>0, :base_fare=>850000, :currency=>"INR"},
  {:amount=>1006500, :gross_amount=>1006500, :tax=>156500, :hotel_fees=>0, :base_fare=>850000, :currency=>"INR"},
]
array_result = main_array.flat_map(&:to_a).group_by(&:first).map do |key, array| 
  { 
    key => (
      result = array.inject(0) do |total, (_, value)| 
        value.is_a?(Fixnum) ? total + value : value
      end 
      result.is_a?(Fixnum) ? result / main_array.size : result 
    ) 
  } 
end
p array_result

edited Jun 28, 2017 at 14:06

answered Jun 13, 2017 at 16:02

Sebastián Palma

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4 Comments

Ravi Over a year ago

What is _ in |_,a,b| doing? Can you please explain?

Ramon Marques Over a year ago

@Ravi it's explained in my answer, first attribute is key, he called it _ second attribute is the old value, or value from the first hash, third attribute is the new value or value from the second hash

Sebastián Palma Over a year ago

_ corresponds to the hash's key, it could be named as you want, but as I'm not using it but it must be references then I assign it as _, that means that's something that's needed to make the block works, but won't be used inside.

Eric Duminil Over a year ago

The question mentions "multiple hashes", not just 2 hashes.

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