Subtract Values in Hash from Corresponding Values in Another Hash

Subtracting Values in two identical hashes in ruby

I would just do:

hash1 = {:total=>{:gold=>100, :dark=>500}, :defensive=>{:gold=>100, :dark=>500}}
hash2 = {:total=>{:gold=>20, :dark=>200}, :defensive=>{:gold=>20, :dark=>200}}

hash1.merge(hash2) { |_, l, r| l.merge(r) { |_, x, y| x - y } }
#=> {:total=>{:gold=>80, :dark=>300}, :defensive=>{:gold=>80, :dark=>300}}

Subtract two hashes in Ruby

Use the reject method:

class Hash
  def difference(other)
    reject do |k,v|
      other.has_key? k
    end
  end
end

To only reject key/value pairs if the values are identical (as per mallanaga's suggestion via a comment on my original answer, which I have deleted):

class Hash
  def difference(other)
    reject do |k,v|
      other.has_key?(k) && other[k] == v
    end
  end
end

---

Subtract values in hash

arr = [
  {:device=>"router", :portmax=>"Port 1/5/3:2006.0", :discardmax=>16617331511, 
     :timeCapturedmax=>"February 18, 2018 at 09:27 AM", :time_unixmax=>1518964024},
  {:device=>"router", :portmax=>"Port 1/5/3:2006.0", :discardmax=>16617216094,
     :timeCapturedmax=>"February 18, 2018 at 09:22 AM", :time_unixmax=>1518963724},
  {:device=>"router", :portmax=>"Port 1/5/3:2006.0", :discardmax=>16617202279,
     :timeCapturedmax=>"February 18, 2018 at 09:18 AM", :time_unixmax=>1518963485},
  {:device=>"router", :portmax=>"Port 1/5/3:2006.0", :discardmax=>16616985649,
     :timeCapturedmax=>"February 18, 2018 at 09:12 AM", :time_unixmax=>1518963135},
  {:device=>"router", :portmax=>"Port 1/5/3:2006.0", :discardmax=>16616404836,
     :timeCapturedmax=>"February 18, 2018 at 09:07 AM", :time_unixmax=>1518962829},
  {:device=>"router", :portmax=>"Port 1/5/3:2006.0", :discardmax=>16616368250,
     :timeCapturedmax=>"February 18, 2018 at 09:03 AM", :time_unixmax=>1518962583}
]

arr.each_cons(2).map do |g,h|
  { device: g[:device], discard_sub: g[:discardmax]-h[:discardmax] }
end
  #=> [{:device=>"router", :discard_sub=>115417},
  #    {:device=>"router", :discard_sub=>13815},
  #    {:device=>"router", :discard_sub=>216630},
  #    {:device=>"router", :discard_sub=>580813},
  #    {:device=>"router", :discard_sub=>36586}]

Check that a hash includes another hash

In Ruby 2.3.

abc.select{|h| h >= ghi}

Note: This was answered before the OP mentioned the Ruby version.

Prior versions of Ruby:

abc.select{|h| h.merge(ghi) == h}

Subtracting from two columns and having the values add up if the name is present more than once

awk to the rescue

awk 'FNR == NR {          # collect the keys and count from first file
   ks[$1]++
   next
}

FNR != NR && FNR==1 {     # when switched to second file, print the counts
   print "\t$VAR1={"      # in the format
   for (k in ks) {
     print "\t\t" k "=>" ks[k] ","
   }
   print "\t};\n"
}

{
   print $3,$4,$5         # print the extract from second file
   if ($5 in ks) {        # and compute the accumulated diffs
     ss[$5] += $4 - $3
   }
}

END {                     # finally, print the accumulated diffs
   print "\n"
   for (s in ss) {
     print s, ss[s]
   }
}' file1 file2

Divide contents of one hash with contents of another in Rails

You can use ActiveRecord::Calculations#average like this:

daily_average = monthly_subscriptions_new.group_by_day(:created_at)
                                         .average(:total_spend)

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