Statistical function which computes the average work time in different months

Question

It's a task from a Ruby-course, in which I'm currently enrolled: Ruby Course - Page

Precisely it's one of the assignments for the first week.

Following idea: Your are given a list in which finished work-tasks are logged. [ {work: "item 1", date: "2017-04-26", time: 20}, {work: "item 2", date: "2017-04-27", time: 27}, ...

You shall write a function which computes the daily work-time for the different months. Means: The average daily work-time in April, avg. time in May, ... in June. And so on ...

A data-structure, to work upon, was given. Even the result, which is expected for that data-structure: { "2017-04" => 40, "2017-05" => 14 }.

I was able to write a function, which passed all unit-tests. Here it is:

#!/usr/bin/ruby
tasks = [
  {work: "item 1", date: "2017-04-26", time: 20},
  {work: "item 2", date: "2017-04-27", time: 27},
  {work: "item 3", date: "2017-04-27", time: 33},
  {work: "item 4", date: "2017-05-05", time: 20},
  {work: "item 5", date: "2017-05-06", time: 12},
  {work: "item 6", date: "2017-05-14", time: 10},
]

# Expected result : { "2017-04" => 40, "2017-05" => 14 }
def work_per_month(tasks)
  days_aggregate = {}

  tasks.each do | task |
    key = task[:date]

    if days_aggregate.key?(key)
      days_aggregate[key][0] = days_aggregate[key][0] + task[:time]
    else
      arr = []
      arr[0] = task[:time]

      days_aggregate[key] = arr
    end
  end

  months_aggregate = {}

  days_aggregate.each do | key, task |
    parts = key.split("-")
    k = "#{parts[0]}-#{parts[1]}"

    if months_aggregate.key?(k)
      months_aggregate[k][0] = months_aggregate[k][0] + task[0]
      months_aggregate[k][1] = months_aggregate[k][1] + 1
    else
      arr = []
      arr[0] = task[0]
      arr[1] = 1

      months_aggregate[k] = arr
    end
  end

  avg_hours_month = {}

  months_aggregate.each do | key, data |
    avg_hours_month[key] = data[0] / data[1]
  end

  avg_hours_month
end

puts work_per_month(tasks)  # Returns {"2017-04"=>40, "2017-05"=>14} 

Please take into account that I started Ruby programming just a week ago.

It works and it has passed the tests. But I'm aware that it is clumsy.

Is there are more elegant way to solve the described task?

Without having this sequence of loops?

Answer 1

Rubocop Report

Rubocop was able to solve minor layout issues regarding the use of white spaces. One note-worthy change it proposed is:

• [Corrected] Style/StringLiterals: Prefer single-quoted strings when you don't need string interpolation or special symbols.

days_aggregate.each do | key, task |
  parts = key.split("-")

 parts = key.split('-')

A bigger complexity issue it found was:

• Metrics/AbcSize: Assignment Branch Condition size for work_per_month is too high. [33/15]
• Metrics/MethodLength: Method has too many lines. [30/10]

This means your method work_per_month is doing way too much. It has more than double the AbcSize than the suggested threshold [33/15]. You should split this method in sub-routines.