Given an array, I need to produce a two-dimensional resulting array where each pair consists of a unique element from the original array and the number of times that element appears. I found two ways to do this. Is one of them better? Is there a better way? arr = %w{a b b c c d e e e} p arr p arr.uniq.map {|e| [e, (arr.select {|ee| ee == e}).size ]} counter = {} arr.each {|e| counter[e] += 1 rescue counter[e] = 1 } p counter.to_a outputs: ["a", "b", "b", "c", "c", "d", "e", "e", "e"] [["a", 1], ["b", 2], ["c", 2], ["d", 1], ["e", 3]] [["a", 1], ["b", 2], ["c", 2], ["d", 1], ["e", 3]]

on 2006-01-09 07:48

on 2006-01-09 11:13

Dan Kohn wrote: > counter = {} > arr.each {|e| counter[e] += 1 rescue counter[e] = 1 } > p counter.to_a > > > outputs: > > ["a", "b", "b", "c", "c", "d", "e", "e", "e"] > [["a", 1], ["b", 2], ["c", 2], ["d", 1], ["e", 3]] > [["a", 1], ["b", 2], ["c", 2], ["d", 1], ["e", 3]] I like #inject 1-liners: >> arr = %w{a b b c c d e e e} => ["a", "b", "b", "c", "c", "d", "e", "e", "e"] >> arr.inject(Hash.new(0)) {|h,x| h[x]+=1;h} => {"a"=>1, "b"=>2, "c"=>2, "d"=>1, "e"=>3} >> arr.inject(Hash.new(0)) {|h,x| h[x]+=1;h}.to_a => [["a", 1], ["b", 2], ["c", 2], ["d", 1], ["e", 3]] >> arr.inject(Hash.new(0)) {|h,x| h[x]+=1;h}.sort => [["a", 1], ["b", 2], ["c", 2], ["d", 1], ["e", 3]] :-) Kind regards robert