How do I generate a random number between 0 and n?
This question is related to
ruby-on-rails
ruby
ruby-on-rails-3
ruby-on-rails-4
random
Don't forget to seed the RNG with srand() first.
Easy way to get random number in ruby is,
def random
(1..10).to_a.sample.to_s
end
Simplest answer to the question:
rand(0..n)
rand(6) #=> gives a random number between 0 and 6 inclusively
rand(1..6) #=> gives a random number between 1 and 6 inclusively
Note that the range option is only available in newer(1.9+ I believe) versions of ruby.
Try array#shuffle method for randomization
array = (1..10).to_a
array.shuffle.first
Don't forget to seed the RNG with srand() first.
You can generate a random number with the rand method. The argument passed to the rand method should be an integer or a range, and returns a corresponding random number within the range:
rand(9) # this generates a number between 0 to 8
rand(0 .. 9) # this generates a number between 0 to 9
rand(1 .. 50) # this generates a number between 1 to 50
#rand(m .. n) # m is the start of the number range, n is the end of number range
If you're not only seeking for a number but also hex or uuid it's worth mentioning that the SecureRandom module found its way from ActiveSupport to the ruby core in 1.9.2+. So without the need for a full blown framework:
require 'securerandom'
p SecureRandom.random_number(100) #=> 15
p SecureRandom.random_number(100) #=> 88
p SecureRandom.random_number #=> 0.596506046187744
p SecureRandom.random_number #=> 0.350621695741409
p SecureRandom.hex #=> "eb693ec8252cd630102fd0d0fb7c3485"
It's documented here: Ruby 1.9.3 - Module: SecureRandom (lib/securerandom.rb)
What about this?
n = 3
(0..n).to_a.sample
Well, I figured it out. Apparently there is a builtin (?) function called rand:
rand(n + 1)
If someone answers with a more detailed answer, I'll mark that as the correct answer.
While you can use rand(42-10) + 10 to get a random number between 10 and 42 (where 10 is inclusive and 42 exclusive), there's a better way since Ruby 1.9.3, where you are able to call:
rand(10...42) # => 13
Available for all versions of Ruby by requiring my backports gem.
Ruby 1.9.2 also introduced the Random class so you can create your own random number generator objects and has a nice API:
r = Random.new
r.rand(10...42) # => 22
r.bytes(3) # => "rnd"
The Random class itself acts as a random generator, so you call directly:
Random.rand(10...42) # => same as rand(10...42)
Notes on Random.new
In most cases, the simplest is to use rand or Random.rand. Creating a new random generator each time you want a random number is a really bad idea. If you do this, you will get the random properties of the initial seeding algorithm which are atrocious compared to the properties of the random generator itself.
If you use Random.new, you should thus call it as rarely as possible, for example once as MyApp::Random = Random.new and use it everywhere else.
The cases where Random.new is helpful are the following:
rand/Random.rand that the main programs might be relying onRandom objects can marshalled)This link is going to be helpful regarding this;
http://ruby-doc.org/core-1.9.3/Random.html
And some more clarity below over the random numbers in ruby;
Generate an integer from 0 to 10
puts (rand() * 10).to_i
Generate a number from 0 to 10 In a more readable way
puts rand(10)
Generate a number from 10 to 15 Including 15
puts rand(10..15)
Non-Random Random Numbers
Generate the same sequence of numbers every time the program is run
srand(5)
Generate 10 random numbers
puts (0..10).map{rand(0..10)}
you can do rand(range)
x = rand(1..5)
While you can use rand(42-10) + 10 to get a random number between 10 and 42 (where 10 is inclusive and 42 exclusive), there's a better way since Ruby 1.9.3, where you are able to call:
rand(10...42) # => 13
Available for all versions of Ruby by requiring my backports gem.
Ruby 1.9.2 also introduced the Random class so you can create your own random number generator objects and has a nice API:
r = Random.new
r.rand(10...42) # => 22
r.bytes(3) # => "rnd"
The Random class itself acts as a random generator, so you call directly:
Random.rand(10...42) # => same as rand(10...42)
Notes on Random.new
In most cases, the simplest is to use rand or Random.rand. Creating a new random generator each time you want a random number is a really bad idea. If you do this, you will get the random properties of the initial seeding algorithm which are atrocious compared to the properties of the random generator itself.
If you use Random.new, you should thus call it as rarely as possible, for example once as MyApp::Random = Random.new and use it everywhere else.
The cases where Random.new is helpful are the following:
rand/Random.rand that the main programs might be relying onRandom objects can marshalled)you can do rand(range)
x = rand(1..5)
How about this one?
num = Random.new
num.rand(1..n)
What about this?
n = 3
(0..n).to_a.sample
Well, I figured it out. Apparently there is a builtin (?) function called rand:
rand(n + 1)
If someone answers with a more detailed answer, I'll mark that as the correct answer.
This link is going to be helpful regarding this;
http://ruby-doc.org/core-1.9.3/Random.html
And some more clarity below over the random numbers in ruby;
Generate an integer from 0 to 10
puts (rand() * 10).to_i
Generate a number from 0 to 10 In a more readable way
puts rand(10)
Generate a number from 10 to 15 Including 15
puts rand(10..15)
Non-Random Random Numbers
Generate the same sequence of numbers every time the program is run
srand(5)
Generate 10 random numbers
puts (0..10).map{rand(0..10)}
You can simply use random_number.
If a positive integer is given as n, random_number returns an integer: 0 <= random_number < n.
Use it like this:
any_number = SecureRandom.random_number(100)
The output will be any number between 0 and 100.
Maybe it help you. I use this in my app
https://github.com/rubyworks/facets
class String
# Create a random String of given length, using given character set
#
# Character set is an Array which can contain Ranges, Arrays, Characters
#
# Examples
#
# String.random
# => "D9DxFIaqR3dr8Ct1AfmFxHxqGsmA4Oz3"
#
# String.random(10)
# => "t8BIna341S"
#
# String.random(10, ['a'..'z'])
# => "nstpvixfri"
#
# String.random(10, ['0'..'9'] )
# => "0982541042"
#
# String.random(10, ['0'..'9','A'..'F'] )
# => "3EBF48AD3D"
#
# BASE64_CHAR_SET = ["A".."Z", "a".."z", "0".."9", '_', '-']
# String.random(10, BASE64_CHAR_SET)
# => "xM_1t3qcNn"
#
# SPECIAL_CHARS = ["!", "@", "#", "$", "%", "^", "&", "*", "(", ")", "-", "_", "=", "+", "|", "/", "?", ".", ",", ";", ":", "~", "`", "[", "]", "{", "}", "<", ">"]
# BASE91_CHAR_SET = ["A".."Z", "a".."z", "0".."9", SPECIAL_CHARS]
# String.random(10, BASE91_CHAR_SET)
# => "S(Z]z,J{v;"
#
# CREDIT: Tilo Sloboda
#
# SEE: https://gist.github.com/tilo/3ee8d94871d30416feba
#
# TODO: Move to random.rb in standard library?
def self.random(len=32, character_set = ["A".."Z", "a".."z", "0".."9"])
chars = character_set.map{|x| x.is_a?(Range) ? x.to_a : x }.flatten
Array.new(len){ chars.sample }.join
end
end
It works fine for me
Well, I figured it out. Apparently there is a builtin (?) function called rand:
rand(n + 1)
If someone answers with a more detailed answer, I'll mark that as the correct answer.
How about this one?
num = Random.new
num.rand(1..n)
Well, I figured it out. Apparently there is a builtin (?) function called rand:
rand(n + 1)
If someone answers with a more detailed answer, I'll mark that as the correct answer.
You can simply use random_number.
If a positive integer is given as n, random_number returns an integer: 0 <= random_number < n.
Use it like this:
any_number = SecureRandom.random_number(100)
The output will be any number between 0 and 100.
If you're not only seeking for a number but also hex or uuid it's worth mentioning that the SecureRandom module found its way from ActiveSupport to the ruby core in 1.9.2+. So without the need for a full blown framework:
require 'securerandom'
p SecureRandom.random_number(100) #=> 15
p SecureRandom.random_number(100) #=> 88
p SecureRandom.random_number #=> 0.596506046187744
p SecureRandom.random_number #=> 0.350621695741409
p SecureRandom.hex #=> "eb693ec8252cd630102fd0d0fb7c3485"
It's documented here: Ruby 1.9.3 - Module: SecureRandom (lib/securerandom.rb)
range = 10..50
rand(range)
or
range.to_a.sample
or
range.to_a.shuffle(this will shuffle whole array and you can pick a random number by first or last or any from this array to pick random one)
Maybe it help you. I use this in my app
https://github.com/rubyworks/facets
class String
# Create a random String of given length, using given character set
#
# Character set is an Array which can contain Ranges, Arrays, Characters
#
# Examples
#
# String.random
# => "D9DxFIaqR3dr8Ct1AfmFxHxqGsmA4Oz3"
#
# String.random(10)
# => "t8BIna341S"
#
# String.random(10, ['a'..'z'])
# => "nstpvixfri"
#
# String.random(10, ['0'..'9'] )
# => "0982541042"
#
# String.random(10, ['0'..'9','A'..'F'] )
# => "3EBF48AD3D"
#
# BASE64_CHAR_SET = ["A".."Z", "a".."z", "0".."9", '_', '-']
# String.random(10, BASE64_CHAR_SET)
# => "xM_1t3qcNn"
#
# SPECIAL_CHARS = ["!", "@", "#", "$", "%", "^", "&", "*", "(", ")", "-", "_", "=", "+", "|", "/", "?", ".", ",", ";", ":", "~", "`", "[", "]", "{", "}", "<", ">"]
# BASE91_CHAR_SET = ["A".."Z", "a".."z", "0".."9", SPECIAL_CHARS]
# String.random(10, BASE91_CHAR_SET)
# => "S(Z]z,J{v;"
#
# CREDIT: Tilo Sloboda
#
# SEE: https://gist.github.com/tilo/3ee8d94871d30416feba
#
# TODO: Move to random.rb in standard library?
def self.random(len=32, character_set = ["A".."Z", "a".."z", "0".."9"])
chars = character_set.map{|x| x.is_a?(Range) ? x.to_a : x }.flatten
Array.new(len){ chars.sample }.join
end
end
It works fine for me
Try array#shuffle method for randomization
array = (1..10).to_a
array.shuffle.first
range = 10..50
rand(range)
or
range.to_a.sample
or
range.to_a.shuffle(this will shuffle whole array and you can pick a random number by first or last or any from this array to pick random one)
Easy way to get random number in ruby is,
def random
(1..10).to_a.sample.to_s
end
Simplest answer to the question:
rand(0..n)
Don't forget to seed the RNG with srand() first.
rand(6) #=> gives a random number between 0 and 6 inclusively
rand(1..6) #=> gives a random number between 1 and 6 inclusively
Note that the range option is only available in newer(1.9+ I believe) versions of ruby.
Source: Stackoverflow.com