This time I will change Ruby code. My little monster looks like this:
def sum_by_column(data)
sum_array = data.group_by do |column|
[column[0], column[2]]
end.values.map { |item| item.transpose[1].inject(:+) }
data.group_by do |column|
[column[0], column[2]]
end.keys.zip(sum_array).map { |first, last| [first[0], last, first[1]] }
end
If You know what this code does I say: Wow! I wrote this code but it’s terrible. I must do something with it. OK, lets start from the beginning. This method gets data as an array of integer arrays. Like this: [[1, 2, 3], [4, 5, 6]]. Then groups the data by first and last column and sums by middle column. When You have data like this:
data = [
[1, 3, 1],
[1, 1, 1],
[1, 1, 2],
[1, 1, 2],
[2, 2, 1]
]
then our method returns
result = [
[1, 4, 1],
[1, 2, 2],
[2, 2, 1]
]
I decided to change this method. On the end I need an array similar to result. So I declared an array. Then I grouped my array by first and last column. Finally I summed the middle column in loop and put all data into array. Now our method looks like this:
def sum_by_column(data)
array = []
grouped_data = data.group_by { |column| [column[0], column[2]] }
grouped_data.each do |key, value|
sum = value.transpose[1].inject(:+)
array << [key.first, sum, key.last]
end
array
end
After that I noticed that order in the data array doesn’t matter. My input and output changed to:
data = [
[1, 1, 3],
[1, 1, 1],
[1, 2, 1],
[1, 2, 1],
[2, 1, 2]
]
result = [
[1, 1, 4],
[1, 2, 2],
[2, 1, 2]
]
The method changed only a little:
def sum_by_column(data)
array = []
grouped_data = data.group_by { |column| column[0..1] }
grouped_data.each do |key, value|
array << (key << value.transpose[2].inject(:+))
end
array
end
OK, it looks better now but what else can I do to improve it? Let me see… Maybe I can replace each with map:
def sum_by_column(data)
grouped_data = data.group_by { |column| column[0..1] }
grouped_data.map { |key, value| [*key, value.transpose[2].inject(:+)] }
end
Yeyyy… It looks fine now. Finally this method is acceptable for me. If you have any suggestions how can I change this method, please left your comment.
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