How to create hash from array

Question

Here is my array:

sorted_array = [["Friday", "42", 8], ["Friday", "34", 8], ["Friday", "41", 78], ["Friday", "35", 7], ["Friday", "40", 7], ["Friday", "36", 6], ["Friday", "39", 7], ["Friday", "37", 56], ["Friday", "38", 6], ["Monday", "38", 3], ["Monday", "39", 5], ["Monday", "37", 54], ["Monday", "40", 6], ["Monday", "36", 6], ["Monday", "41", 7], ["Monday", "35", 7], ["Monday", "42", 7], ["Monday", "34", 8]]

I need to make:

{ 'Friday' => [ ["42", 8], ["34", 8], ["41", 78], ["35", 7], [ "40", 7], ["36", 6], [ "39", 7], ["37", 56], [ "38", 6] ]  }

The same with "Monday".Can someone shed a light on this?

This is how I get the data from POST:

{"0"=>{"Monday"=>{"34"=>8}, "Friday"=>{"34"=>8}}, "1"=>{"Monday"=>{"35"=>7}, "Friday"=>{"35"=>7}}, "2"=>{"Monday"=>{"36"=>6}, "Friday"=>{"36"=>6}}, "3"=>{"Monday"=>{"37"=>54}, "Friday"=>{"37"=>56}}, "4"=>{"Monday"=>{"38"=>3}, "Friday"=>{"38"=>6}}, "5"=>{"Monday"=>{"39"=>5}, "Friday"=>{"39"=>7}}, "6"=>{"Monday"=>{"40"=>6}, "Friday"=>{"40"=>7}}, "7"=>{"Monday"=>{"41"=>7}, "Friday"=>{"41"=>78}}, "8"=>{"Monday"=>{"42"=>7}, "Friday"=>{"42"=>8}}}

Then I turn it into array and sorted:

 hash_array = []
 specific_ranges.each do |key, value|
   value.each do |day, scores|
      scores.each do |a_score, amount|
         hash_array.push [day, a_score, amount]
      end
   end
 end

Sorted:

sorted_array = hash_array.sort_by &:first

hirolau · Accepted Answer · 2015-02-12 12:02:54Z

5

Ruby MAGIC:

p sorted_array.group_by(&:shift) #=> {"Friday"=>[["42", 8], ["34", 8], ["41", 78], ["35", 7] ...

Explanation: shift gets the first value of the array and at the same time removes it from the array, so the group_by function produce exactly what you are looking for.

edited Feb 12, 2015 at 12:02

answered Feb 12, 2015 at 9:52

hirolau

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1 Comment

Mr H Over a year ago

Yes. This is lovely, you cleaver cookie. Thanks mate.

shivam · Accepted Answer · 2015-02-12 06:19:56Z

you can try something like this directly to your data:

data = {"0"=>{"Monday"=>{"34"=>8}, "Friday"=>{"34"=>8}}, "1"=>{"Monday"=>{"35"=>7}, "Friday"=>{"35"=>7}}, "2"=>{"Monday"=>{"36"=>6}, "Friday"=>{"36"=>6}}, "3"=>{"Monday"=>{"37"=>54}, "Friday"=>{"37"=>56}}, "4"=>{"Monday"=>{"38"=>3}, "Friday"=>{"38"=>6}}, "5"=>{"Monday"=>{"39"=>5}, "Friday"=>{"39"=>7}}, "6"=>{"Monday"=>{"40"=>6}, "Friday"=>{"40"=>7}}, "7"=>{"Monday"=>{"41"=>7}, "Friday"=>{"41"=>78}}, "8"=>{"Monday"=>{"42"=>7}, "Friday"=>{"42"=>8}}}

a ||= Hash.new { |h, k| h[k] = [] }   
data.each{ |d|
  d[1].keys.each { |key|
    a[key] << d[1][key]
  }
}

a
# => {"Monday"=>[{"34"=>8}, {"35"=>7}, {"36"=>6}, {"37"=>54}, {"38"=>3}, {"39"=>5}, {"40"=>6}, {"41"=>7}, {"42"=>7}], "Friday"=>[{"34"=>8}, {"35"=>7}, {"36"=>6}, {"37"=>56}, {"38"=>6}, {"39"=>7}, {"40"=>7}, {"41"=>78}, {"42"=>8}]}

You can improve the result further by using Array#uniq for array of hashes if required.

Santhosh · Accepted Answer · 2015-02-12 06:17:34Z

1

 sorted_array.group_by(&:first).map { |k, v| [k, v.map { |a| a[1..-1] }] }.to_h
 # {"Friday"=>[["42", 8], ["34", 8], ["41", 78], ["35", 7], ["40", 7], ["36", 6], ["39", 7], ["37", 56], ["38", 6]],
 #  "Monday"=>[["38", 3], ["39", 5], ["37", 54], ["40", 6], ["36", 6], ["41", 7], ["35", 7], ["42", 7], ["34", 8]]}

answered Feb 12, 2015 at 6:17

Santhosh

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Comments

sawa · Accepted Answer · 2015-02-12 06:28:55Z

1

h = sorted_array.group_by(&:first).each_value{|a| a.each(&:shift)}

h.select{|k, _| k == "Friday"}
#=> { 'Friday' => [ ["42", 8], ["34", 8], ["41", 78], ["35", 7], [ "40", 7], ["36", 6], [ "39", 7], ["37", 56], [ "38", 6] ]  }

answered Feb 12, 2015 at 6:28

sawa

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Comments

Deepesh · Accepted Answer · 2015-02-12 06:09:48Z

I have a quick solution for you. This may not be the optimal but here it is:

sorted_array = [["Friday", "42", 8], ["Friday", "34", 8], ["Friday", "41", 78], ["Friday", "35", 7], ["Friday", "40", 7], ["Friday", "36", 6], ["Friday", "39", 7], ["Friday", "37", 56], ["Friday", "38", 6], ["Monday", "38", 3], ["Monday", "39", 5], ["Monday", "37", 54], ["Monday", "40", 6], ["Monday", "36", 6], ["Monday", "41", 7], ["Monday", "35", 7], ["Monday", "42", 7], ["Monday", "34", 8]]

s = sorted_array.select{|x| x[0] == 'Friday'}.each{|a| a.shift}

Hash['Friday', s]

This will return the result as you require. But while doing it I found a limitation that the line of code:

s = sorted_array.select{|x| x[0] == 'Friday'}.each{|a| a.shift}

is running just a single time and it will return a blank array if you run it the second time consecutively. So if you use this please take care of that. Hope this helps.

Aleksei Matiushkin · Accepted Answer · 2015-02-12 06:21:01Z

This is a standard task for Array#reduce.

sorted_array.reduce({}) { |memo, e| 
  (memo[e.first] ||= []) << e[1..-1]
  memo 
}

Here we fulfill the hash with the rest of every array element, using first elements as keys.

UPD Actually, you don’t need to reorganize your hash, everything might be done within one step:

h = {"0"=>{"Monday"=>{"34"=>8}, "Friday"=>{"34"=>8}}, "1"=>{"Monday"=>{"35"=>7}, "Friday"=>{"35"=>7}}, "2"=>{"Monday"=>{"36"=>6}, "Friday"=>{"36"=>6}}, "3"=>{"Monday"=>{"37"=>54}, "Friday"=>{"37"=>56}}, "4"=>{"Monday"=>{"38"=>3}, "Friday"=>{"38"=>6}}, "5"=>{"Monday"=>{"39"=>5}, "Friday"=>{"39"=>7}}, "6"=>{"Monday"=>{"40"=>6}, "Friday"=>{"40"=>7}}, "7"=>{"Monday"=>{"41"=>7}, "Friday"=>{"41"=>78}}, "8"=>{"Monday"=>{"42"=>7}, "Friday"=>{"42"=>8}}}
h.reduce({}) { |memo, k| 
  k.last.each { |k,v| (memo[k] ||= []) << v.to_a.flatten }
  memo 
}

Cary Swoveland · Accepted Answer · 2015-02-12 08:42:38Z

0

Two for the price of one:

#1

arr.each_with_object({}) { |a,h| h.update(a.shift=>[a]) { |_,o,n| o+n } }

#2

h = arr.group_by(&:first)
h.each { |k,v| h[k] = v.transpose[1..-1].transpose }

edited Feb 12, 2015 at 8:42

answered Feb 12, 2015 at 8:18

Cary Swoveland

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