To sum up more than one array values in hash - Ruby

Question

I have a hash example which has two element (section_one and section_two) in Ruby. I want to sum up each element separately and estimate each element average.

My hash:

class_grades = {
  :section_one => [88, 74, 64],
  :section_two => [99, 100]
}

I have tried on this code

sum = 0
class_grades.each do |key, value|
  value.each do |value1|
    sum += value1
  end
    puts "#{key}: #{sum.to_f}"
end

but it turns out with the result:

section_one: 226.0
section_two: 425.0

I have a problem to sum up each element separately. It estimates firs element and goes on. Could you help me to fix this problem.

Answer 1

First, with minimum editing of your code:

class_grades.each do |key, value|
  sum = 0
  value.each do |value1|
    sum += value1
  end
    puts "#{key}: #{sum.to_f}"
end

But I'll recommend you do someth about:

class_grades.each do |key, value|
  puts "#{key}: #{value.inject(:+).to_f}"
end

Answer 2

You should set to zero sum at the beginning of your loop

class_grades.each do |key, value|
  sum = 0
  value.each do |value1|
    sum += value1
  end
  puts "#{key}: #{sum.to_f}"
end

There is a more idiomatic way to get the sum from an enumerable

class_grades.each do |key, value|
  sum = value.inject(0, :+)
  puts "#{key}: #{sum.to_f}"
end

And, you don't need that .to_f . 1 + 2.5 gets 3.5

class_grades.each do |key, value|
  sum = value.inject(0, :+)
  puts "#{key}: #{sum}"
end

Answer 3

Here's another way to do this:

class_grades.map { |k,v| [k, v.sum.fdiv(v.size).round(1)] }.to_h
 #=> { :section_one => 75.3, :section_two => 99.5 }

Key methods: Array#sum (>2.4.0), Integer#fdiv and Float#round . See ruby-doc.org for more info.