Question

I am new to ruby and looking for an elegant way to sort the following hash.

Hash A:

a = { :metric1 => {
          "Bob" =>10,
          "Jane" =>15,
          "Sally" =>20
      },                
      :metric2 => {  
          "Jane" =>15,
          "Bob" =>10,
          "Sally" =>10 
      },         
      :metric3 => {  
          "Bob" =>10,
          "Sally" =>10,
          "Jane" =>5
      }
    }

Hash B:

b = { "Bob" => {
        :metric1 =>10,
        :metric2 =>10,
        :metric3 =>10
      },
      "Jane" => {
        :metric1 =>15,
        :metric2 =>15,
        :metric3 =>5
      },
      "Sally" => {
        :metric1 =>20,
        :metric2 =>10,
        :metric3 =>10
      }
    }

Essentially I want an easy way to iterate this object to output a table like:

        Metric 1  Metric 2  Metric 3
Bob     10        20        20
Jane    15        15        5
Sally   20        10        10

Answer 1

Functional approach (assumes all people have the same metric keys):

names = a.values.first.keys
b = Hash[names.map do |name| 
  [name, Hash[a.map { |metric, values| [metric, values[person]] }]]
end]

[Edit] A second approach, proably more orthodox than my first attempt. It uses Facets (so it may look a bit cryptic for those unfamiliar the new abstractions it procides). However, it’s easy if you check the output of each step:

triplets = a.flat_map { |metric, h| h.map { |name, value| [name, metric, value] } }
pairs_by_name = triplets.map_by { |name, metric, value| [name, [metric, value]] }
b = pairs_by_name.mash { |name, pairs| [name, pairs.to_h] }