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rubyarrayshashenumerable

Convert Array to Hash removing duplicate keys and adding values at the same time

I have an array that looks like so:

f = [["Wed, 12-31", 120.0],["Thu, 01-01", 120.0], ["Thu, 01-01", 120.0]]

I can convert it to a hash and remove the duplicate keys:

h = Hash[ *f.collect { |v| [v] }.flatten ]
# => {"Wed, 12-31"=>120.0, "Thu, 01-01"=>120.0}

which is almost there, but I'd like to sum the value for elements with the identical date strings, the desired result from the above array would be this:

{"Wed, 12-31"=>120.0, "Thu, 01-01"=>240.0}

How can I accomplish this?

Solution

  • This works:

    result = Hash.new(0)
f = [["Wed, 12-31", 120.0],["Thu, 01-01", 120.0], ["Thu, 01-01", 120.0]]
f.each { |subarray| result[subarray[0]] += subarray[1] }
puts result

    If you would like to be fancy you could use .inject()