Question

I have an embedded hash, for which i need to calculate averages. I’ve already grouped them, successfully, (from ungrouped) but finding the average isn’t working for me

Here is the example hash data

myhash = {"2011-02-15"=>[["2011-02-15", 10], ["2011-02-15", 60]], 
          "2011-02-22"=>[["2011-02-22", 22]], 
          "2011-02-28"=>[["2011-02-28", 110],["2011-02-28", 70]]}

here is how I grouped them (they used to be just {k => v} ungrouped)

@r = @myhash.group_by(&:first)

I tried both solutions from this thread (What's the best way in Ruby to average sets in an array?) but neither worked.

good question. I want the results to be averaged by date, so I can serve them up that way.

[{"2012-02-15" => 35"}, {"2012-02-22" => 22"}, {"2012-02-28" => 90"}]

Answer 1

Hash[myhash.map { |k,v| [k, v.map(&:last).inject(:+) / v.size] }]
#=> {"2011-02-15"=>35, "2011-02-22"=>22, "2011-02-28"=>90}