Hey all, using ruby 1.8.7, I wrote this:
500.times.map { Integer((rand * 1) * 1000) / Float(1000) }
Basically, this gives me a list of 500 random decimal numbers that are
rounded to 3 places. However, I also want to make sure that all are
unique.
thanks for response
--
You received this message because you are subscribed to the Google Groups
"Ruby on Rails: Talk" group.
To post to this group, send email to
rubyonrails-talk-/JYPxA39Uh5TLH3MbocFF+G/Ez6ZCGd0@public.gmane.org
To unsubscribe from this group, send email to
rubyonrails-talk+unsubscribe-/JYPxA39Uh5TLH3MbocFF+G/Ez6ZCGd0@public.gmane.org
For more options, visit this group at
http://groups.google.com/group/rubyonrails-talk?hl=en.
> 500.times.map { Integer((rand * 1) * 1000) / Float(1000) } > > Basically, this gives me a list of 500 random decimal numbers that are > rounded to 3 places. However, I also want to make sure that all are > unique.Tack a .uniq to the end... http://ruby-doc.org/core-1.9.3/Array.html#method-i-uniq -philip -- You received this message because you are subscribed to the Google Groups "Ruby on Rails: Talk" group. To post to this group, send email to rubyonrails-talk-/JYPxA39Uh5TLH3MbocFF+G/Ez6ZCGd0@public.gmane.org To unsubscribe from this group, send email to rubyonrails-talk+unsubscribe-/JYPxA39Uh5TLH3MbocFF+G/Ez6ZCGd0@public.gmane.org For more options, visit this group at http://groups.google.com/group/rubyonrails-talk?hl=en.
On Tue, Feb 28, 2012 at 7:10 PM, John Merlino <stoicism1-YDxpq3io04c@public.gmane.org> wrote:> Hey all, using ruby 1.8.7, I wrote this: > > 500.times.map { Integer((rand * 1) * 1000) / Float(1000) } > > Basically, this gives me a list of 500 random decimal numbers that are > rounded to 3 places. However, I also want to make sure that all are > unique. > > thanks for response > > -- > You received this message because you are subscribed to the Google Groups "Ruby on Rails: Talk" group. > To post to this group, send email to rubyonrails-talk-/JYPxA39Uh5TLH3MbocFF+G/Ez6ZCGd0@public.gmane.org > To unsubscribe from this group, send email to rubyonrails-talk+unsubscribe@googlegroups.com. > For more options, visit this group at http://groups.google.com/group/rubyonrails-talk?hl=en. >Here is one thing that comes to mind a = (1..1000).to_a a.shuffle! pick 1st 500 a[0,500] last 500 item from the list a[-500..-1] If you want you can call shuffle a few times, see what works best for you. -- Kind Regards, Rajinder Yadav SafetyNet Test Driven Development http://safetynet.devmentor.org -- You received this message because you are subscribed to the Google Groups "Ruby on Rails: Talk" group. To post to this group, send email to rubyonrails-talk-/JYPxA39Uh5TLH3MbocFF+G/Ez6ZCGd0@public.gmane.org To unsubscribe from this group, send email to rubyonrails-talk+unsubscribe@googlegroups.com. For more options, visit this group at http://groups.google.com/group/rubyonrails-talk?hl=en.
On 29.02.2012, at 4:10, John Merlino wrote:> Hey all, using ruby 1.8.7, I wrote this: > > 500.times.map { Integer((rand * 1) * 1000) / Float(1000) } > > Basically, this gives me a list of 500 random decimal numbers that are > rounded to 3 places. However, I also want to make sure that all are > unique..uniq() doesn''t guarentee 500 number exactly. .shuffle() just tosses the collection and doesn''t give you unique numbers. You''d better to implement method: def secure(number, precision) collection = [] collection |= [SecureRandom.random_number.round(precision)] while collection.size < number collection end> secure(500, 3)=> collection of 500 unique random numbers. -- You received this message because you are subscribed to the Google Groups "Ruby on Rails: Talk" group. To post to this group, send email to rubyonrails-talk-/JYPxA39Uh5TLH3MbocFF+G/Ez6ZCGd0@public.gmane.org To unsubscribe from this group, send email to rubyonrails-talk+unsubscribe-/JYPxA39Uh5TLH3MbocFF+G/Ez6ZCGd0@public.gmane.org For more options, visit this group at http://groups.google.com/group/rubyonrails-talk?hl=en.
On Tue, Feb 28, 2012 at 8:03 PM, Valery Kvon <addager-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org> wrote:> On 29.02.2012, at 4:10, John Merlino wrote: > >> Hey all, using ruby 1.8.7, I wrote this: >> >> 500.times.map { Integer((rand * 1) * 1000) / Float(1000) } >> >> Basically, this gives me a list of 500 random decimal numbers that are >> rounded to 3 places. However, I also want to make sure that all are >> unique. > > .uniq() doesn''t guarentee 500 number exactly. > .shuffle() just tosses the collection and doesn''t give you unique numbers. > > You''d better to implement method: > > def secure(number, precision) > collection = [] > collection |= [SecureRandom.random_number.round(precision)] while collection.size < number > collection > end > >> secure(500, 3) > => collection of 500 unique random numbers. >Sweet! -- You received this message because you are subscribed to the Google Groups "Ruby on Rails: Talk" group. To post to this group, send email to rubyonrails-talk-/JYPxA39Uh5TLH3MbocFF+G/Ez6ZCGd0@public.gmane.org To unsubscribe from this group, send email to rubyonrails-talk+unsubscribe@googlegroups.com. For more options, visit this group at http://groups.google.com/group/rubyonrails-talk?hl=en.
Valery Kvon wrote in post #1049372:> You''d better to implement method: > > def secure(number, precision) > collection = [] > collection |= [SecureRandom.random_number.round(precision)] while > collection.size < number > collection > end > >> secure(500, 3) > => collection of 500 unique random numbers.One simple way to get what you want is by using a set: Here''s your method of generating random numbers. Don''t count on it giving you "secure" random numbers, but this technique won''t care how you produced them. #!/usr/bin/env ruby require ''set'' def random_numbers(n = 500) my_set = Set.new while my_set.size < 500 value = Integer((rand * 1) * 1000) / Float(1000) my_set << value end my_set.to_a end puts random_numbers.size -- Posted via http://www.ruby-forum.com/. -- You received this message because you are subscribed to the Google Groups "Ruby on Rails: Talk" group. To post to this group, send email to rubyonrails-talk-/JYPxA39Uh5TLH3MbocFF+G/Ez6ZCGd0@public.gmane.org To unsubscribe from this group, send email to rubyonrails-talk+unsubscribe-/JYPxA39Uh5TLH3MbocFF+G/Ez6ZCGd0@public.gmane.org For more options, visit this group at http://groups.google.com/group/rubyonrails-talk?hl=en.
Robert Walker wrote in post #1049376:> #!/usr/bin/env ruby > require ''set'' > > def random_numbers(n = 500) > my_set = Set.new > while my_set.size < 500 > value = Integer((rand * 1) * 1000) / Float(1000) > my_set << value > end > my_set.to_a > end > > puts random_numbers.sizeOne caveat with this technique: Make sure you build in some "circuit breaker" protection code. The more numbers you ask this to generate the more rounds it will take to produce the result. Generating 500 unique numbers is averaging about 700 rounds. The closer to 1000 you get the more rounds it will take. Over 1000 and it will never finish. -- Posted via http://www.ruby-forum.com/. -- You received this message because you are subscribed to the Google Groups "Ruby on Rails: Talk" group. To post to this group, send email to rubyonrails-talk-/JYPxA39Uh5TLH3MbocFF+G/Ez6ZCGd0@public.gmane.org To unsubscribe from this group, send email to rubyonrails-talk+unsubscribe-/JYPxA39Uh5TLH3MbocFF+G/Ez6ZCGd0@public.gmane.org For more options, visit this group at http://groups.google.com/group/rubyonrails-talk?hl=en.
On 29 February 2012 00:10, John Merlino <stoicism1-YDxpq3io04c@public.gmane.org> wrote:> 500.times.map { Integer((rand * 1) * 1000) / Float(1000) } > > Basically, this gives me a list of 500 random decimal numbers that are > rounded to 3 places. However, I also want to make sure that all are > unique.This is a classic "how do I achieve my solution?", rather than a "here''s my problem... how can I solve it" post... Can we back up a second please? What are you trying to achieve with this list of 500 numbers? And what do you want to do if the list you have generated does contain duplicates? As already said, you can use the .uniq method to remove dupes - but that might leave you with an array of 496 elements... would that be a problem? Are you really asking "how do I generate an array of 500 random numbers"? What do you want to do with these 500 random numbers? Considering that one user could make a request and get their 500 randoms, and another user could do the same - there could be duplicates across users. Is this going to be a problem? Please try to ask clearer questions, as the way it stands, I could spend ages of my time coming up with solutions to what I *think* is your problem, just to have you say "nope... that''s not what I was after". Multiply that across the subscribers to this list, and you''ve wasted a hell of a lot of peoples'' time around the world :-/ PS BTW Why are you multiplying by 1 in your example code? (and does that line even work if you paste it into your console, as it explodes for me with a LocalJumpError... but that may just be Ruby versions...) -- You received this message because you are subscribed to the Google Groups "Ruby on Rails: Talk" group. To post to this group, send email to rubyonrails-talk-/JYPxA39Uh5TLH3MbocFF+G/Ez6ZCGd0@public.gmane.org To unsubscribe from this group, send email to rubyonrails-talk+unsubscribe@googlegroups.com. For more options, visit this group at http://groups.google.com/group/rubyonrails-talk?hl=en.
Peter Vandenabeele
2012-Feb-29 08:51 UTC
Re: Re: ensuring random list of numbers are unique
On Wed, Feb 29, 2012 at 3:05 AM, Robert Walker <lists-fsXkhYbjdPsEEoCn2XhGlw@public.gmane.org> wrote:> Robert Walker wrote in post #1049376: > > #!/usr/bin/env ruby > > require ''set'' > > > > def random_numbers(n = 500) > > my_set = Set.new > > while my_set.size < 500 > > value = Integer((rand * 1) * 1000) / Float(1000) > > my_set << value > > end > > my_set.to_a > > end > > > > puts random_numbers.size > > One caveat with this technique: Make sure you build in some "circuit > breaker" protection code. The more numbers you ask this to generate the > more rounds it will take to produce the result. Generating 500 unique > numbers is averaging about 700 rounds. The closer to 1000 you get the > more rounds it will take. Over 1000 and it will never finish. >Another caveat is that the Array contains "Float" objects, while the original question was "500 unique decimals". Two issues here: 1) if "decimals" are asked in the problem statement, why then do we serve Floats in the result? 2) The problem is that for uniqueness, we need the ''=='' operator and on Floats that represent fractional numbers in the decimal system, equality is not a stable function (as was discussed many times before ...). So, in all proposed solutions, I would exchange this line:> value = Integer((rand * 1) * 1000) / Float(1000)with this one: value = rand(1000) / BigDecimal.new(1000) HTH, Peter -- You received this message because you are subscribed to the Google Groups "Ruby on Rails: Talk" group. To post to this group, send email to rubyonrails-talk-/JYPxA39Uh5TLH3MbocFF+G/Ez6ZCGd0@public.gmane.org To unsubscribe from this group, send email to rubyonrails-talk+unsubscribe-/JYPxA39Uh5TLH3MbocFF+G/Ez6ZCGd0@public.gmane.org For more options, visit this group at http://groups.google.com/group/rubyonrails-talk?hl=en.
thanks for responses, the ultimate goal was just to ensure a list of 500 (no more or less) unique random decimals that are 3 places which would be generated only one time. Currently Im storing them as a float in the mysql database. -- You received this message because you are subscribed to the Google Groups "Ruby on Rails: Talk" group. To post to this group, send email to rubyonrails-talk-/JYPxA39Uh5TLH3MbocFF+G/Ez6ZCGd0@public.gmane.org To unsubscribe from this group, send email to rubyonrails-talk+unsubscribe-/JYPxA39Uh5TLH3MbocFF+G/Ez6ZCGd0@public.gmane.org For more options, visit this group at http://groups.google.com/group/rubyonrails-talk?hl=en.
On 1 March 2012 01:05, John Merlino <stoicism1-YDxpq3io04c@public.gmane.org> wrote:> thanks for responses, the ultimate goal was just to ensure a list of > 500 (no more or less) unique random decimals that are 3 places which > would be generated only one time. Currently Im storing them as a float > in the mysql database.One time for ever? You do realise there''s only 1000 numbers between 0 and 0.999? After two runs, you''ll have used up the whole pool. -- You received this message because you are subscribed to the Google Groups "Ruby on Rails: Talk" group. To post to this group, send email to rubyonrails-talk-/JYPxA39Uh5TLH3MbocFF+G/Ez6ZCGd0@public.gmane.org To unsubscribe from this group, send email to rubyonrails-talk+unsubscribe-/JYPxA39Uh5TLH3MbocFF+G/Ez6ZCGd0@public.gmane.org For more options, visit this group at http://groups.google.com/group/rubyonrails-talk?hl=en.
Peter Vandenabeele
2012-Mar-01 08:57 UTC
Re: Re: ensuring random list of numbers are unique
On Thu, Mar 1, 2012 at 2:05 AM, John Merlino <stoicism1-YDxpq3io04c@public.gmane.org> wrote:> thanks for responses, the ultimate goal was just to ensure a list of > 500 (no more or less) unique random decimals that are 3 places which > would be generated only one time. Currently I''m storing them as a float > in the mysql database. >Do yourself a favor and change your migration with a line like this: t.decimal :number, :precision => 10, :scale => 3 That''s all it takes to use decimals (with 3 digits following the decimal point) in the database too. HTH, Peter -- You received this message because you are subscribed to the Google Groups "Ruby on Rails: Talk" group. To post to this group, send email to rubyonrails-talk-/JYPxA39Uh5TLH3MbocFF+G/Ez6ZCGd0@public.gmane.org To unsubscribe from this group, send email to rubyonrails-talk+unsubscribe-/JYPxA39Uh5TLH3MbocFF+G/Ez6ZCGd0@public.gmane.org For more options, visit this group at http://groups.google.com/group/rubyonrails-talk?hl=en.