Ruby - Show Deltas Between two arrays of hashes based on a subset of hash keys

Question

Ruby - Show Deltas Between two arrays of hashes based on a subset of hash keys

I'm trying to compare two arrays of hashes with a very similar hash structure (identical and always present keys) and return the delta between them - in particular, I would like to capture the following:

Hashes a part array1

that does not exist inarray2
Hashes a part array2

that does not exist inarray1
Hashes that appear in both datasets

This can usually be achieved by simply doing the following:

deltas_old_new = (array1-array2)
deltas_new_old = (array2-array1)

The problem for me (which turned into a 2-3 hour struggle!) Is that I need to determine the delta based on the values of 3 keys in the hash ("id", "ref", 'name') - the values of these 3 The -x keys actually make up what makes up the unique entry in my data - but I have to keep other hash key / value pairs (for example, 'extra'

and many other key / value pairs not shown for brevity.

Sample data:

array1 = [{'id' => '1', 'ref' => '1001', 'name' => 'CA', 'extra' => 'Not Sorted On 5'},
          {'id' => '2', 'ref' => '1002', 'name' => 'NY', 'extra' => 'Not Sorted On 7'},
          {'id' => '3', 'ref' => '1003', 'name' => 'WA', 'extra' => 'Not Sorted On 9'},
          {'id' => '7', 'ref' => '1007', 'name' => 'OR', 'extra' => 'Not Sorted On 11'}]

array2 = [{'id' => '1', 'ref' => '1001', 'name' => 'CA', 'extra' => 'Not Sorted On 5'},
          {'id' => '3', 'ref' => '1003', 'name' => 'WA', 'extra' => 'Not Sorted On 9'},
          {'id' => '8', 'ref' => '1002', 'name' => 'NY', 'extra' => 'Not Sorted On 7'},
          {'id' => '5', 'ref' => '1005', 'name' => 'MT', 'extra' => 'Not Sorted On 10'},
          {'id' => '12', 'ref' => '1012', 'name' => 'TX', 'extra' => 'Not Sorted On 85'}]

Expected result (3 separate arrays of hashes):

An object containing data in array1

, but not in array2

-

[{'id' => '2', 'ref' => '1002', 'name' => 'NY', 'extra' => 'Not Sorted On 7'},
 {'id' => '7', 'ref' => '1007', 'name' => 'OR', 'extra' => 'Not Sorted On 11'}]

An object containing data in array2

, but not in array1

-

[{'id' => '8', 'ref' => '1002', 'name' => 'NY', 'extra' => 'Not Sorted On 7'},
 {'id' => '5', 'ref' => '1005', 'name' => 'MT', 'extra' => 'Not Sorted On 10'},
 {'id' => '12', 'ref' => '1012', 'name' => 'TX', 'extra' => 'Not Sorted On 85'}]

Object containing data in BOTH array1

and array2

-

[{'id' => '1', 'ref' => '1001', 'name' => 'CA', 'extra' => 'Not Sorted On 5'},
 {'id' => '3', 'ref' => '1003', 'name' => 'WA', 'extra' => 'Not Sorted On 9'}]

I have tried many attempts at comparing iteration over arrays and using Hash#keep_if

based on 3 keys, and also merging both datasets into one array, and then trying deduplication based on array1

, but I keep going empty handed. Thank you in advance for your time and help!

+3

set ruby

Kurt W Jul 26 17 at 20:12

source to share

3 answers

For this type of problem, it is usually easier to work with indexes.

code

def keepers(array1, array2, keys)
  a1 = make_hash(array1, keys)
  a2 = make_hash(array2, keys)
  common_keys_of_a1_and_a2 = a1.keys & a2.keys
  [keeper_idx(array1, a1, common_keys_of_a1_and_a2),
   keeper_idx(array2, a2, common_keys_of_a1_and_a2)]
end

def make_hash(arr, keys)
  arr.each_with_index.with_object({}) do |(g,i),h|
    (h[g.values_at(*keys)] ||= []) << i
  end
end

def keeper_idx(arr, a, common_keys_of_a1_and_a2)
  arr.size.times.to_a - a.values_at(*common_keys_of_a1_and_a2).flatten
end

Example

array1 =
  [{'id' =>  '1', 'ref' => '1001', 'name' => 'CA', 'extra' => 'Not Sorted On 5'},
   {'id' =>  '2', 'ref' => '1002', 'name' => 'NY', 'extra' => 'Not Sorted On 7'},
   {'id' =>  '3', 'ref' => '1003', 'name' => 'WA', 'extra' => 'Not Sorted On 9'},
   {'id' =>  '3', 'ref' => '1003', 'name' => 'WA', 'extra' => 'Not Sorted On 8'},
   {'id' =>  '7', 'ref' => '1007', 'name' => 'OR', 'extra' => 'Not Sorted On 11'}]

array2 =
  [{'id' =>  '1', 'ref' => '1001', 'name' => 'CA', 'extra' => 'Not Sorted On 5'},
   {'id' =>  '3', 'ref' => '1003', 'name' => 'WA', 'extra' => 'Not Sorted On 9'},
   {'id' =>  '8', 'ref' => '1002', 'name' => 'NY', 'extra' => 'Not Sorted On 7'},
   {'id' =>  '5', 'ref' => '1005', 'name' => 'MT', 'extra' => 'Not Sorted On 10'},
   {'id' =>  '5', 'ref' => '1005', 'name' => 'MT', 'extra' => 'Not Sorted On 12'},
   {'id' => '12', 'ref' => '1012', 'name' => 'TX', 'extra' => 'Not Sorted On 85'}]

Please note that the two arrays are slightly different from those in the question. The question did not indicate if each array two hashes have the same values for the specified keys. So I added a hash for each array to show if the case is.

keys = ['id', 'ref', 'name']

idx1, idx2 = keepers(array1, array2, keys)
  #=> [[1, 4], [2, 3, 4, 5]]

idx1

( idx2

) are the indices of the elements array1

( array2

) that remain after the matches are removed. ( array1

and array2

do not change.)

It follows that the two arrays are mapped to

array1.values_at(*idx1)
  #=> [{"id"=> "2", "ref"=>"1002", "name"=>"NY", "extra"=>"Not Sorted On 7"},
  #    {"id"=> "7", "ref"=>"1007", "name"=>"OR", "extra"=>"Not Sorted On 11"}]

and

array2.values_at(*idx2)
  #=> [{"id"=> "8", "ref"=>"1002", "name"=>"NY", "extra"=>"Not Sorted On 7"},
  #    {"id"=> "5", "ref"=>"1005", "name"=>"MT", "extra"=>"Not Sorted On 10"},
  #    {"id"=> "5", "ref"=>"1005", "name"=>"MT", "extra"=>"Not Sorted On 12"},
  #    {"id"=>"12", "ref"=>"1012", "name"=>"TX", "extra"=>"Not Sorted On 85"}]

The hash values to be removed are set as follows.

array1.size.times.to_a - idx1
  #=> [0, 2, 3]
array2.size.times.to_a - idx2
  #[0, 1]

Explanation

Following are the steps.

a1 = make_hash(array1, keys)
  #=> {["1", "1001", "CA"]=>[0], ["2", "1002", "NY"]=>[1],
  #    ["3", "1003", "WA"]=>[2, 3], ["7", "1007", "OR"]=>[4]}    
a2 = make_hash(array2, keys)
  #=> {["1", "1001", "CA"]=>[0], ["3", "1003", "WA"]=>[1],
  #    ["8", "1002", "NY"]=>[2], ["5", "1005", "MT"]=>[3, 4],
  #    ["12", "1012", "TX"]=>[5]}
common_keys_of_a1_and_a2 = a1.keys & a2.keys
  #=> [["1", "1001", "CA"], ["3", "1003", "WA"]]
keeper_idx(array1, a1, common_keys_of_a1_and_a2)
  #=> [1, 4] (for array1)
keeper_idx(array2, a2, common_keys_of_a1_and_a2)
  #=> [2, 3, 4, 5]· (for array2)

+1

Cary swoveland Aug 29. 17 at 23:01

source to share

See Array#-

andArray#&

array1 - array2   #data in array1 but not in array2
array2 - array1   #data in array2 but not in array1
array1 & array2   #data in both array1 and array2

Since you tagged this question set you can use kits in a similar way:

require 'set'

set1 = array1.to_set
set2 = array2.to_set

set1 - set2
set2 - set1
set1 & set2

0

Sagar Pandya Jul 26 17 at 20:24

source to share

Simple Lime · Accepted Answer · 2017-07-26T20:47:35+0000

It's not pretty, but it works. It creates a third array of all the unique values array1

and array2

and iterate through it.

Then, since it include?

doesn't allow for a custom match, we can fake it by detect

and search for an element in the array that has a custom sub-hash match. We'll wrap this in a custom method so we can just call it passing in array1

or array2

instead of writing twice.

Finally, we loop through ours array3

and determine if it came item

from array1

, array2

or both and add to the appropriate output array.

array1 = [{'id' => '1', 'ref' => '1001', 'name' => 'CA', 'extra' => 'Not Sorted On 5'},
          {'id' => '2', 'ref' => '1002', 'name' => 'NY', 'extra' => 'Not Sorted On 7'},
          {'id' => '3', 'ref' => '1003', 'name' => 'WA', 'extra' => 'Not Sorted On 9'},
          {'id' => '7', 'ref' => '1007', 'name' => 'OR', 'extra' => 'Not Sorted On 11'}]

array2 = [{'id' => '1', 'ref' => '1001', 'name' => 'CA', 'extra' => 'Not Sorted On 5'},
          {'id' => '3', 'ref' => '1003', 'name' => 'WA', 'extra' => 'Not Sorted On 9'},
          {'id' => '8', 'ref' => '1002', 'name' => 'NY', 'extra' => 'Not Sorted On 7'},
          {'id' => '5', 'ref' => '1005', 'name' => 'MT', 'extra' => 'Not Sorted On 10'},
          {'id' => '12', 'ref' => '1012', 'name' => 'TX', 'extra' => 'Not Sorted On 85'}]

# combine the arrays into 1 array that contains items in both array1 and array2 to loop through
array3 = (array1 + array2).uniq { |item| { 'id' => item['id'], 'ref' => item['ref'], 'name' => item['name'] } }

# Array#include? doesn't allow a custom matcher, so we can fake it by using Array#detect
def is_included_in(array, object)
  object_identifier = { 'id' => object['id'], 'ref' => object['ref'], 'name' => object['name'] }

  array.detect do |item|
    { 'id' => item['id'], 'ref' => item['ref'], 'name' => item['name'] } == object_identifier
  end
end

# output array initializing
array1_only = []
array2_only = []
array1_and_array2 = []

# loop through all items in both array1 and array2 and check if it was in array1 or array2
# if it was in both, add to array1_and_array2, otherwise, add it to the output array that
# corresponds to the input array
array3.each do |item|
  in_array1 = is_included_in(array1, item)
  in_array2 = is_included_in(array2, item)

  if in_array1 && in_array2
    array1_and_array2.push item
  elsif in_array1
    array1_only.push item
  else
    array2_only.push item
  end
end


puts array1_only.inspect        # => [{"id"=>"2", "ref"=>"1002", "name"=>"NY", "extra"=>"Not Sorted On 7"}, {"id"=>"7", "ref"=>"1007", "name"=>"OR", "extra"=>"Not Sorted On 11"}]
puts array2_only.inspect        # => [{"id"=>"8", "ref"=>"1002", "name"=>"NY", "extra"=>"Not Sorted On 7"}, {"id"=>"5", "ref"=>"1005", "name"=>"MT", "extra"=>"Not Sorted On 10"}, {"id"=>"12", "ref"=>"1012", "name"=>"TX", "extra"=>"Not Sorted On 85"}]
puts array1_and_array2.inspect  # => [{"id"=>"1", "ref"=>"1001", "name"=>"CA", "extra"=>"Not Sorted On 5"}, {"id"=>"3", "ref"=>"1003", "name"=>"WA", "extra"=>"Not Sorted On 9"}]

Ruby - Show Deltas Between two arrays of hashes based on a subset of hash keys

More articles: