# Changing an array data structure **URL:** \ **Category:** Ruby\ **Created:** [January 24, 2008, 4:05pm UTC](https://www.ruby-forum.com/t/changing-an-array-data-structure/127045 "2008-01-24T16:05:50Z")\ **Posts on this page:** 3\ **Page:** 1
**Author:** ![wickie](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/w/ba9def/32.png) [@wickie](https://www.ruby-forum.com/u/wickie)\ **Post date:** [January 24, 2008, 4:05pm UTC](https://www.ruby-forum.com/t/changing-an-array-data-structure/127045/1 "2008-01-24T16:05:50Z")
Hello. I already asked about how I’d best re-order a datastructure. But thinking about, I changed my mind; instead of the hash approach I’ve shown in news:removed\_email\_address@domain.invalid, I now think I might use arrays instead. Reason: The order in which something is inserted and later fetched is important to me. With Hashes in 1.8, this cannot easily be done out-of-the-box, can it? Anyway - I’m now looking for a way to change the following arry: timing = [ [“Performance Test of Item Access using Lists”, [ [[“Plants”, 100], [“Customers”, 50], [“Total”, 150]], [[“Plants”, 85], [“Customers”, 60], [“Total”, 145]], [[“Plants”, 111], [“Customers”, 77], [“Total”, 188]] ]], [“Performance Test of Item Access using Advance Item Search”, [ [[“Work List”, 17], [“Bookmarks”, 30], [“Total”, 42]], [[“Work List”, 10], [“Bookmarks”, 33], [“Total”, 50]], [[“Work List”, 22], [“Bookmarks”, 27], [“Total”, 99]] ]] ] # This should become: timing\_reordered = [ [“Performance Test of Item Access using Lists”, [ [“Plants”, [100, 85, 111]], [“Customers”, [50, 60, 77]], [“Total”, [150, 145, 188]] ]], [“Performance Test of Item Access using Advance Item Search”, [ [“Work List”, [17, 10, 22]], [“Bookmarks”, [30, 33, 27]], [“Total”, [42, 50, 99]] ]] ] It very much resembles the datastructure shown in the hash approach. That’s only natural, if you take into consideration how the data is generated. To do that, I’m running a method 3 (or more) times; these methods generate the “Performance Test of Item Access using Lists” and “Performance Test of Item Access using Advance Item Search” data. These methods generate data; data items for Plants, Customers and so on. But for reporting, it’s best for me, if all the eg. Plants results are “grouped together”. Actually, I only need the innermost arrays, ie. [100, 85, 111], [50, 60, 77], … These arrays should be concated, so that I’ve only got one long array, starting with: [100, 85, 111, 50, 60, 77, …]. Well - how would I reorder the array best? I tried: ``` timing.each { |test| ... } ``` But actually, I already fail to go on there. Now “test” is an array. When I access test[0], I get the “category labels” (“Performance Test of …”) and with test[1], I get the entries. Ie.: ``` Plants 100 Customers 50 Total 150 ``` If I add another “each loop” into that existing loop, I don’t get what I’d expect. I tried: ``` timing.each { |test| test[1].each { |test_values| puts test_values[0] } } ``` Now I’d expect to get Plants, Customers, Total, Work Lists, Bookmarks, Total. But I get: ``` Plants 100 Plants 85 Plants 111 Work List 17 Work List 10 Work List 22 ``` So I only get the 1st “column” of the input data. Why’s that? And how would I do that correctly, as that’s obviously not the right way to go? Thanks again, Michael ---
**Author:** ![wickie](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/w/ba9def/32.png) [@wickie](https://www.ruby-forum.com/u/wickie)\ **Post date:** [January 25, 2008, 3:37pm UTC](https://www.ruby-forum.com/t/changing-an-array-data-structure/127045/2 "2008-01-25T15:37:46Z")
2008/1/24, Michael S. [removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid): > Hello. > > I already asked about how I’d best re-order a datastructure. But > thinking about, I changed my mind; instead of the hash approach > I’ve shown in news:removed\_email\_address@domain.invalid, > I now think I might use arrays instead. Reason: The order in which > something is inserted and later fetched is important to me. With > Hashes in 1.8, this cannot easily be done out-of-the-box, can it? > > Anyway - I’m now looking for a way to change the following arry: This is not an Array but an object graph composed of nested Arrays. > ``` > ]] > > ``` > > ] > > # This should become: > > timing\_reordered = [ > [“Performance Test of Item Access using Lists”, [ > [“Plants”, [100, 85, 111]], [“Customers”, [50, 60, 77]], [“Total”, [150, 145, 188]] > ]], > [“Performance Test of Item Access using Advance Item Search”, [ > [“Work List”, [17, 10, 22]], [“Bookmarks”, [30, 33, 27]], [“Total”, [42, 50, 99]] > ]] > ] My first advice would be to use proper data types, e.g. S1 = Struct.new :plants, :customers, :total S2 = Struct.new :work\_list, :bookmarks, :total etc. > It very much resembles the datastructure shown in the hash approach. > That’s only natural, if you take into consideration how the data is > generated. To do that, I’m running a method 3 (or more) times; these > methods generate the “Performance Test of Item Access using Lists” > and “Performance Test of Item Access using Advance Item Search” data. For these you should use those structs (see above). > These methods generate data; data items for Plants, Customers and > so on. > > But for reporting, it’s best for me, if all the eg. Plants results > are “grouped together”. Actually, I only need the innermost arrays, > ie. [100, 85, 111], [50, 60, 77], … These arrays should be > concated, so that I’ve only got one long array, starting with: [100, > 85, 111, 50, 60, 77, …]. With the structs above # data contains S1 data.inject(S1.new) do |s,d| (s.plants ||= []) \<\< d.plants (s.customers ||= []) \<\< d.customers (s.total ||= []) \<\< d.total s end Alternatively data.inject(:plants=\>[], :customers=\>[], :total=\>[]) do |s,d| d.members.each {|m| s[m.to\_sym] = d[m]} s end Of course you need to take additional measures to cope with the nesting (S1 and S2). Cheers robert ---
**Author:** ![wickie](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/w/ba9def/32.png) [@wickie](https://www.ruby-forum.com/u/wickie)\ **Post date:** [January 25, 2008, 4:35pm UTC](https://www.ruby-forum.com/t/changing-an-array-data-structure/127045/3 "2008-01-25T16:35:33Z")
Robert K. [removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid) wrote: > > Anyway - I’m now looking for a way to change the following arry: > > [[“Work List”, 17], [“Bookmarks”, 30], [“Total”, 42]], > > [“Performance Test of Item Access using Advance Item Search”, [ > > [“Work List”, [17, 10, 22]], [“Bookmarks”, [30, 33, 27]], > > [[“Total”, [42, 50, 99]] > > ]] > > ] > > My first advice would be to use proper data types, e.g. > > S1 = Struct.new :plants, :customers, :total > S2 = Struct.new :work\_list, :bookmarks, :total Can I automatically create those elements of the Struct? I don’t want to have to fiddle with the data type, when a new test comes up. And I’d also like to have easy access to the name of the test in a well written way (ie. “Work List”). How do I iterate over the elements of the Struct? I absolutely do not want to have to rely on knowing the names of all these data points. I think I’d be all set, if I could use hashes, because then I’d have all I need - but in Ruby 1.8, the order of the elements of a hash is not “stable”. Ie., I “insert” “Work List”, “Bookmarks” and “Total”, but when I iterate over the hash, I get back “Bookmarks”, “Work List” and “Total” ☹ No good ☹ As I don’t want to lose the order in which something has been added to the datastructure, I’m forced to use arrays in Ruby 1.8, aren’t I? […] > With the structs above > > # data contains S1 > > data.inject(S1.new) do |s,d| > (s.plants ||= []) \<\< d.plants > (s.customers ||= []) \<\< d.customers > (s.total ||= []) \<\< d.total Urgs. I don’t want to have to know that there’s a “plants”, “customers”, “total”, etc.pp… Thanks a lot, Michael