how to count array of hash based some values in ruby?

Question

hi how to count array of hash based some values in ruby?

example :

gundams = [{:type=>"perfect grade", :name=>"00 raiser gundam 1/60"}, {:type=>"perfect grade", :name=>"strike freedom gundam 1/60"}, {:type=>"perfect grade", :name=>"astray red flame gundam 1/60"}, {:type=>"master grade", :name=>"exia gundam 1/100"}, {:type=>"master grade", :name=>"wing zero costum 1/100"}]

how to count array of hash based type? i want get result like this :

{"perfect grade"=>3, "master grade"=>2}

thanks before

falsetru · Accepted Answer · 2014-03-07 08:29:04Z

2

Using Enumerable#group_by:

gundams = [
  {:type=>"perfect grade", :name=>"00 raiser gundam 1/60"},
  {:type=>"perfect grade", :name=>"strike freedom gundam 1/60"},
  {:type=>"perfect grade", :name=>"astray red flame gundam 1/60"},
  {:type=>"master grade", :name=>"exia gundam 1/100"},
  {:type=>"master grade", :name=>"wing zero costum 1/100"}
]
Hash[gundams.group_by {|g| g[:type]}.map {
  |type, gs| [type, gs.size]
}]
# => {"perfect grade"=>3, "master grade"=>2}

edited Mar 7, 2014 at 8:29

answered Mar 7, 2014 at 8:15

falsetru

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5 Comments

tardjo Over a year ago

i mean result like this {"perfect grade"=>3, "master grade"=>2}, sorry not add string. thank you for you answer, already right :)

falsetru Over a year ago

@tardjo, I see. I updated the answer according to the question edit.

tardjo Over a year ago

hi @falsetru how to convert result to [3,2] ?

falsetru Over a year ago

@tardjo, Use Hash#values: Hash[gundams.group_by {|g| g[:type]}.map { |type, gs| [type, gs.size] }].values

falsetru Over a year ago

@tardjo, If you don't need the hash at all, just: gundams.group_by {|g| g[:type]}.map { |type, gs| gs.size }

Abdo · Accepted Answer · 2014-03-07 08:19:28Z

1

As suggested by @falsetru (who was faster), use Enumerable#group_by

gundams.group_by { |e| e[:type] }.map { |k,v| [k, v.length] }
=> [["perfect grade", 3], ["master grade", 2]]

You can then print the array above as you wish.

answered Mar 7, 2014 at 8:19

Abdo

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Comments

Martin · Accepted Answer · 2014-03-07 08:16:47Z

0

Something like this?

gundams = [{:type=>"perfect grade", :name=>"00 raiser gundam 1/60"}, {:type=>"perfect grade", :name=>"strike freedom gundam 1/60"}, {:type=>"perfect grade", :name=>"astray red flame gundam 1/60"}, {:type=>"master grade", :name=>"exia gundam 1/100"}, {:type=>"master grade", :name=>"wing zero costum 1/100"}]

# Create a hash with a 0 as default value
total = Hash.new(0)

# Iterate on each value and increment for its type
gundams.each { |value| total[value[:type]] += 1 }

p total
# => {"perfect grade"=>3, "master grade"=>2}

answered Mar 7, 2014 at 8:16

Martin

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1 Comment

tardjo Over a year ago

hi @Martin how to convert result to array like this [3,2] ?

bjhaid · Accepted Answer · 2014-03-07 09:46:33Z

0

Different approach to solving the problem with Enumerable#each_with_object

gundams.each_with_object(Hash.new(0)) { |x,hash| hash[x[:type]] += 1 }
#=> {"perfect grade"=>3, "master grade"=>2}

answered Mar 7, 2014 at 9:46

bjhaid

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