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How can I produce a random number in a range from 1 million to 10 million?

rand(10) works, I tried rand(1..10) and that didn't work.

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6 Answers 6

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13

Take your base number, 1,000,000 and add a random number from 0 up to your max - starting number:

 1_000_000 + Random.rand(10_000_000 - 1_000_000) #=> 3084592
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5 Comments

I'm using ruby 1.8.7, Random doesnt' seem to exist. is it a gem?
@Blankman: Did you try require 'random', and also checking if it's 1.9.2 only?
1.8.7 doesn't have Random. It's in 1.9.2+. Install the backports gem and you'll inherit it in 1.8.7, along with lots of other juicy goodness.
what are the ramifications of installing backport? (if any)
Just use rand, not Random.rand. It works all the way back as far as 1.6.0
6

It's an instance method:

puts Random.new.rand(1_000_000..10_000_000-1)
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1_000_000...10_000_000 is more Ruby-ish.
3

I find this more readable:

7.times.map { rand(1..9) }.join.to_i
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1

This will generate a random number between 1,000,000 and 9,999,999.

rand(10_000_000-1_000_000)+1_000_000

This works in 1.8.7 without any gems(backports, etc).

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Or, in case performance is not an issue and you don't want to count zeros:

(0...7).map { |i| rand((i == 0 ? 1 : 0)..9) }.join.to_i
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Needed a way to avoid zeros
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Another option with ruby 1.8.7 compatibility:

rand(9999999999).to_s.center(10, rand(9).to_s).to_i

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