How to build unique array of objects with condition in ruby

Question

I have an array of objects and want to build an unique array by the attribute "position", like

boxes.to_a.uniq! {|p| p[:position] }

but i want to distinguish before throwing all the doubles away, if the second attribute "mismatch" is equal or higher. For example i have:

{ position: 233, mismatch: 3},
{ position: 234, mismatch: 3},
{ position: 233, mismatch: 1}

and in the end i'd like to keep the one with less mismatch:

{ position: 234, mismatch: 3},
{ position: 233, mismatch: 1}

because position was the same in object 1 and 3, but mismatch was less in the last object.

Edit: boxes is an array of objects and i build it like that:

@boxes = []

...

@boxes << {
              :position => i,
              :mismatch => mm,
          }

where position and mismatch is calculated over a DNA sequence. The mismatch represents the hamming distance to a 9-nucleotide motif ( string like "TTGATGCTT" )

What is boxes originally? Hashes can't have duplicate keys anyways, so this is a bit confusing. — squiguy
– squiguy, Commented May 11, 2013 at 23:37

Aaron K · Accepted Answer · 2013-05-11 23:39:09Z

3

I'm not sure what these hashes represent, so you can probably think of better variable names.

Try:

boxes = [
  { position: 233, mismatch: 3},
  { position: 234, mismatch: 3},
  { position: 233, mismatch: 1},
]

boxes.group_by{ |box| box[:position] }
     .map{ |_, boxes| boxes.min_by{ |box| box[:mismatch] } }
#=> [{:position=>233, :mismatch=>1}, {:position=>234, :mismatch=>3}]

answered May 11, 2013 at 23:39

Aaron K

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Comments

Vlad the Impala · Accepted Answer · 2013-05-11 23:35:25Z

0

Something like this:

new_boxes = {}

boxes.each do |box|
  pos = box[:position]
  if new_boxes[pos] && new_boxes[pos][:mismatch] > box[:mismatch]
    new_boxes[pos] = box
  end
end

boxes = new_boxes.values

answered May 11, 2013 at 23:35

Vlad the Impala

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Comments

Arup Rakshit · Accepted Answer · 2013-05-12 09:34:00Z

0

boxes = [
  { position: 233, mismatch: 1},
  { position: 234, mismatch: 3},
  { position: 233, mismatch: 3},
  { position: 234, mismatch: 2}
]

boxes.sort_by{|x| x.values }
     .uniq{|y| y[:position]}

#=> [{:position=>233, :mismatch=>1}, {:position=>234, :mismatch=>2}]

edited May 12, 2013 at 9:34

answered May 12, 2013 at 9:18

Arup Rakshit

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