How to condense summable metrics to a unique identifier in a ruby table

Question

I\'m trying to condense summable metrics to a unique identifier in a ruby table.

I have the following table:

[[\"id1\", 123], [\"id2\", 234], [\"id1\", 3         


        

Answer 1

I think the other answerers are overthinking this. You can do this with just one operation, each_with_object, and a Hash:

metrics = [["id1", 123], ["id2", 234], ["id1", 345]]

metrics.each_with_object(Hash.new(0)) do |(id, val), sums|
  sums[id] += val
end
# => {"id1"=>468, "id2"=>234}

If you want an Array instead of a Hash at the end just call to_a on the result, but there are few compelling reasons to do so.

Answer 2

As condensed as it can get.

array = [["id1", 123],["id2", 234], ["id1", 345]]
array.group_by(&:first).collect{|key,values| [key,values.reduce(0) {|sum,a| sum+a[1]}]}

Answer 3

summable_metrics = [["id1", 123],["id2", 234], ["id1", 345]]

summable_metrics.group_by(&:first).map do |k, v|
  [k, v.map(&:last).reduce(:+)]
end

=> [["id1", 468], ["id2", 234]]