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Editorial Team
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Asked: 2026-05-26T23:47:37+00:00

I am working on a program that will compare two .csv files. After extracting

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I am working on a program that will compare two .csv files. After extracting the relevant data from one of the csv files into an array of arrays, I need to combine related entries. For example, I would want to turn this array:

[["11/13/15", ["4001", "1392"], "INBOUND"], 
["11/13/15", ["4090", "540"], "INBOUND"], 
["11/13/15", ["1139", "162"], "INBOUND"], 
["11/13/15", ["1158", "64"], "INBOUND"], 
["11/13/15", ["4055", "352"], "OUTBOUND"], 
["11/13/15", ["4055", "448"], "OUTBOUND"], 
["11/13/15", ["4055", "352"], "OUTBOUND"], 
["11/13/15", ["1139", "162"], "OUTBOUND"], 
["11/13/15", ["1158", "64"], "OUTBOUND"], 
["11/13/15", ["4091", "520"], "OUTBOUND"]]

into this:

[["11/13/15", ["4001", "1392"], "INBOUND"], 
["11/13/15", ["4090", "540"], "INBOUND"], 
["11/13/15", ["1139", "162"], "INBOUND"], 
["11/13/15", ["1158", "64"], "INBOUND"], 
["11/13/15", ["4055", "1152"], "OUTBOUND"], 
["11/13/15", ["1139", "162"], "OUTBOUND"], 
["11/13/15", ["1158", "64"], "OUTBOUND"], 
["11/13/15", ["4091", "520"], "OUTBOUND"]]

For some element of the array, if its items at [0], [1][0], and [2] match those of another one, then create a new item (array) with its item at [1][1] being the sum of all the items at [1][1] and delete the old arrays. If it would be easier, I can change the way the relevant data is extracted so that the item at [1] is not an array and each row has 4 items instead of 3.

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1 Answer

  1. Editorial Team

    I assume that the elements to group are consecutive so we can use Enumerable#chunk. Functional approach:

    grouped_xs = xs.chunk { |date, (id1, id2), direction| [date, id1, direction] }
grouped_xs.map do |(date, id1, direction), ary|
  id2_sum = ary.map { |date, (id1, id2), direction| id2.to_i }.inject(:+)
  [date, id1, id2_sum.to_s, direction]
end

    Output (you wanted 4 elements in the output array, right?):

    [["11/13/15", "4001", "1392", "INBOUND"],
 ["11/13/15", "4090", "540", "INBOUND"],
 ["11/13/15", "1139", "162", "INBOUND"],
 ["11/13/15", "1158", "64", "INBOUND"],
 ["11/13/15", "4055", "1152", "OUTBOUND"],
 ["11/13/15", "1139", "162", "OUTBOUND"],
 ["11/13/15", "1158", "64", "OUTBOUND"],
 ["11/13/15", "4091", "520", "OUTBOUND"]]
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