# Hash or array? **URL:** \ **Category:** Ruby\ **Created:** [September 21, 2009, 6:05pm UTC](https://www.ruby-forum.com/t/hash-or-array/175861 "2009-09-21T18:05:10Z")\ **Posts on this page:** 7\ **Page:** 1
**Author:** ![nescripter](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/n/2acd7d/32.png) [@nescripter](https://www.ruby-forum.com/u/nescripter)\ **Post date:** [September 21, 2009, 6:05pm UTC](https://www.ruby-forum.com/t/hash-or-array/175861/1 "2009-09-21T18:05:10Z")
Hello, I have a question, I want to store some data in two columns, for example 0001, stuff1 stuff2 0002, morestuff 0003, extrastuff 0004, more evenmore As you can see column 1 is an ID and column 2 is one or more strings. I want to do a search across another data set to say if column 1 (ID number) matches in both sets and the contents of column 2 to data set B. I initially thought to use a hash, but it scrambles the order of the data so was unsure of its efficiency and use. Any suggestions? Many thanks ---
**Author:** ![nescripter](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/n/2acd7d/32.png) [@nescripter](https://www.ruby-forum.com/u/nescripter)\ **Post date:** [September 21, 2009, 6:29pm UTC](https://www.ruby-forum.com/t/hash-or-array/175861/2 "2009-09-21T18:29:13Z")
On Mon, Sep 21, 2009 at 10:05 AM, Ne Scripter \< removed\_email\_address@domain.invalid\> wrote: > Posted via [http://www.ruby-forum.com/](http://www.ruby-forum.com/). I’m not sure I completely understand what you are trying to do but with hashes you could do the following: search\_value = 0003 if hash[search\_value] == second\_hash[search\_value] send ahead end if the key doesn’t exist the value will be nil so you might want a special case for that. – “Hey brother Christian with your high and mighty errand, Your actions speak so loud, I can’t hear a word you’re saying.” -Greg Graffin (Bad Religion) ---
**Author:** ![nescripter](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/n/2acd7d/32.png) [@nescripter](https://www.ruby-forum.com/u/nescripter)\ **Post date:** [September 21, 2009, 6:37pm UTC](https://www.ruby-forum.com/t/hash-or-array/175861/3 "2009-09-21T18:37:25Z")
On Mon, Sep 21, 2009 at 6:05 PM, Ne Scripter [removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid) wrote: > I want to do a search across another data set to say if column 1 (ID > number) matches in both sets and the contents of column 2 to data set B. You can do like this to obtain the keys that are common in both sets, then iterate them doing something with the values (in my example add the values from the second to the first, not sure if that’s what you want): irb(main):001:0\> h1 = Hash[1,“a”,2,“b”,3,“c”] =\> {1=\>“a”, 2=\>“b”, 3=\>“c”} irb(main):002:0\> h2 = Hash[1,“x”,3,“y”] =\> {1=\>“x”, 3=\>“y”} irb(main):004:0\> (h1.keys & h2.keys).each {|key| h1[key] += h2[key]} =\> [1, 3] irb(main):005:0\> h1 =\> {1=\>“ax”, 2=\>“b”, 3=\>“cy”} > I initially thought to use a hash, but it scrambles the order of the > data so was unsure of its efficiency and use. If you want to keep the order then you will need to sort the keys, but you can do that after the operation. About efficiency: the hash is good for key access (amortized O(1)), although in this case it only helps in the last step (adding the values), as you need to make the intersection of all the keys first. Hope this helps, Jesus. ---
**Author:** ![nescripter](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/n/2acd7d/32.png) [@nescripter](https://www.ruby-forum.com/u/nescripter)\ **Post date:** [September 21, 2009, 6:30pm UTC](https://www.ruby-forum.com/t/hash-or-array/175861/4 "2009-09-21T18:30:58Z")
Hi, Am Dienstag, 22. Sep 2009, 01:05:12 +0900 schrieb Ne Scripter: > I have a question, I want to store some data in two columns, for example > > 0001, stuff1 stuff2 > 0002, morestuff > 0003, extrastuff > 0004, more evenmore > > I initially thought to use a hash, but it scrambles the order of the > data so was unsure of its efficiency and use. Be aware that Array alway assigns all members from [0] to [max]. a = [] a[5] = :five a #=\> [nil, nil, nil, nil, nil, :five] To keep the order in Hashes, sort the keys: h = { 1 =\> :a, 2 =\> :b } h.keys.sort { |k| h[k] … } # or even h.sort.each { |k,v| … } In Ruby 1.9 the order will be preserved, so just assign ascendingly. Bertram ---
**Author:** ![nescripter](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/n/2acd7d/32.png) [@nescripter](https://www.ruby-forum.com/u/nescripter)\ **Post date:** [September 21, 2009, 8:19pm UTC](https://www.ruby-forum.com/t/hash-or-array/175861/5 "2009-09-21T20:19:18Z")
> I want to do a search across another data set to say if column 1 (ID > number) matches in both sets and the contents of column 2 to data set B. > > I initially thought to use a hash, but it scrambles the order of the > data so was unsure of its efficiency and use. > > Any suggestions? Since everybody else is rooting for hashes, let’s talk arrays. You could use a structure like this: mydata = [nil, [stuff1, stuff2], [morestuff], [extrastruff], [more evenmore]] Then to search for matches, you can do: searched1 = mydata[1] & datasetA & datasetB searched2 = mydata[2] & datasetB This is assuming that your datasets are arrays of course. And it’s fine if you want to use hashes to store the key as id too: mydata ={ 1 =\> [stuff1, stuff2], 2 =\>[morestuff], 3 =\> [extrastruff], 4 =\>[more evenmore] } searched1 = mydata[1] & datasetA & datasetB searched2 = mydata[2] & datasetB ---
**Author:** ![nescripter](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/n/2acd7d/32.png) [@nescripter](https://www.ruby-forum.com/u/nescripter)\ **Post date:** [September 22, 2009, 12:01am UTC](https://www.ruby-forum.com/t/hash-or-array/175861/6 "2009-09-22T00:01:45Z")
On 21.09.2009 18:05, Ne Scripter wrote: > number) matches in both sets and the contents of column 2 to data set B. > > I initially thought to use a hash, but it scrambles the order of the > data so was unsure of its efficiency and use. > > Any suggestions? I think you got some useful recommendations yet. I still have some doubts whether I understand your requirements properly. If you want to determine whether set B is a subset of A you can also do something like this: require ‘set’ YourData = Struct.new :id, :text set\_a = File.readlines(“a.dat”). map {|l| l.chomp!; YourData.new(\*line.split(/,/, 2)}. to\_set set\_b = File.readlines(“b.dat”). map {|l| l.chomp!; YourData.new(\*line.split(/,/, 2)}. to\_set if set\_a.superset? set\_b puts “all b are there” end Kind regards robert ---
**Author:** ![nescripter](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/n/2acd7d/32.png) [@nescripter](https://www.ruby-forum.com/u/nescripter)\ **Post date:** [September 21, 2009, 6:46pm UTC](https://www.ruby-forum.com/t/hash-or-array/175861/7 "2009-09-21T18:46:19Z")
Look up ‘facet/dictionary’ – for a hash that can be sorted / keeps the order.