Calculate Percentage in Ruby

Calculate percentage in ruby?

You mean like this percentage = a/b*100?

Update based on your new description:

class Numeric
  def percent_of(n)
    self.to_f / n.to_f * 100.0
  end
end

# Note: the brackets () around number are optional
p (1).percent_of(10)    # => 10.0  (%)
p (200).percent_of(100) # => 200.0 (%)
p (0.5).percent_of(20)  # => 2.5   (%)

pizza_slices = 5
eaten = 3
p eaten.percent_of(pizza_slices) # => 60.0 (%)

Based on Mladen's code.

How to calculate percentages with rounding

OK, I think we can separate two answers here. First of all, you have to pay attention with rounding and truncating values. It could be dangerous in terms of inconsistent information. Anyways, based on your case, here it is.

• If you want to display only integers and ignore the decimal part of the number, you can use either ceil or floor

  0.47939999999999994.ceil 
  #=> 1
  
  0.47939999999999994.floor 
  #=> 0
  

• If you want to round your decimal, you can use round passing the precision desired:

  0.47939999999999994.round
  #=> 0
  
  0.47939999999999994.round(1)
  #=> 0.5
  
  0.47939999999999994.round(2) 
  #=> 0.48
  
  0.47939999999999994.round(3)
  #=> 0.479
  
  0.47939999999999994.round(4)
  #=> 0.4794
  

Your method should look like the following (using round)

def self.percent
  ((Order.revenue.to_f.round(2) / Order.goal.to_f.round(2)) * 100).round(2)
end

I hope it helps !

Ruby calculate the percentage of elements in hash

You can use Enumerable#each_with_object:

sum = a.values.inject(0, :+) # or simply a.values.sum if you're on Ruby 2.4+
#=> 12
a.each_with_object({}) { |(k, v), hash| hash[k] = v * 100.0 / sum }
#=> {"str1"=>16.666666666666668, "str2"=>25.0, "str3"=>58.333333333333336}

To have it with %:

a.each_with_object({}) { |(k, v), hash| hash[k] = "#{(v * 100.0 / sum).round(2)}%" }
#=> {"str1"=>"16.67%", "str2"=>"25.0%", "str3"=>"58.33%"}

Calculating percentage returns integer

Cast one of price or discount_percentage to float:

price*(discount_percentage.to_f/100)

Number of Percentage in Ruby on Rails

Your discount percentage calculation is off. You need to find the difference between the original price and the new price. And divide it by the original price to get the discount percentage:

def percentage_off
   (Float(original_deal - our_deal) / original_deal * 100).ceil
end

Your input example would now return (100 - 90) / 100 * 100 = 10

Percentage Calculation - Ruby on Rails

How about:

percentages = p.towns.group_by(&:ocean).map {|ocean, towns| [ocean, (towns.count/p.towns.count.to_f * 100).round(0)]}.to_h
perentages.each {|ocean, percentage| puts "Ocean #{ocean}: #{percentage}%"}

How to convert float to percentage in Ruby

To convert a float to a percentage, multiply the float by 100. If you need to output it with the % sign, use string interpolation inside a string.

Example:

percentage_value  = 0.02 * 100
puts "#{percentage_value}%"

2.0%

{edited}

how to calculate percentage for nested fields in ruby on rails

There is child_index thing that rails provide in nested association when using in html.erb.

Below code may resolve your problem.

<div class="education_<%= f.options[:child_index] %>">
  <div class="form-group">
      <%= f.label :max_marks %><br>
      <%= f.text_field :max_marks, class: 'max_marks', data: {index: f.options[:child_index]} %>
    </div>
    <div class="form-group">
      <%= f.label :marks_obtained %><br>
      <%= f.text_field :marks_obtained, class: 'marks_obtained', data: {index: f.options[:child_index]}%>
    </div>
    <div class="form-group">
      <%= f.label :percentage %><br>
      <%= f.text_field :percentage, class: 'percentage' %>
    </div>
</div>

$('.max_marks, .marks_obtained').focusout(function(event){
      var target = $(event.target), parent = target.parents().find('.education_' + target.attr('data-index'));
      if (parseInt(parent.find('.marks_obtained').val()) > parseInt(parent.find('.max_marks').val())){
         alert('Marks Obtained cannot be greater then Maximun Marks');
         parent.find('.marks_obtained').val('');
      } else {
        var max_marks = parseFloat(parent.find('.max_marks').val())
        var marks_obtained = parseFloat(parent.find('.marks_obtained').val())

max_marks = max_marks === NaN ? 0 : max_marks

marks_obtained = marks_obtained === NaN ? 0 : marks_obtained
        parent.find('.percentage').val(marks_obtained * 100 / max_marks)
      }
    });

Ruby calculate percentages of array objects

I would use the group by function:

 my_array = ["one", "two", "two", "three"]
 percentages = Hash[array.group_by{|x|x}.map{|x, y| [x, 1.0*y.size/my_array.size]}]
 p  percentages #=> {"one"=>0.25, "two"=>0.5, "three"=>0.25}
 final = array.map{|x| percentages[x]}
 p final #=> [0.25, 0.5, 0.5, 0.25]

Alternative 2 without group_by:

array, result = ["one", "two", "two", "three"], Hash.new
array.uniq.each  do |number|
  result[number] = array.count(number)
end
p array.map{|x| 1.0*result[x]/array.size}  #=> [0.25, 0.5, 0.5, 0.25]

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