# Looking for something similar to in\_groups\_of but not really **URL:** \ **Category:** Rails\ **Created:** [April 2, 2008, 7:29pm UTC](https://www.ruby-forum.com/t/looking-for-something-similar-to-in-groups-of-but-not-really/133700 "2008-04-02T19:29:33Z")\ **Posts on this page:** 8\ **Page:** 1
**Author:** ![jjkiesch](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/j/bc79bd/32.png) [@jjkiesch](https://www.ruby-forum.com/u/jjkiesch)\ **Post date:** [April 2, 2008, 7:29pm UTC](https://www.ruby-forum.com/t/looking-for-something-similar-to-in-groups-of-but-not-really/133700/1 "2008-04-02T19:29:33Z")
i’m trying to figure out an elegant way of taking an array or enumerable object and dividing it as even as possible into sub arrays. in\_groups\_of works fine if i’m trying to define the number of objects inside each sub array, but what if i just want to define how many sub arrays instead? is there a method for something like that or would i need to write something custom? ---
**Author:** ![jjkiesch](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/j/bc79bd/32.png) [@jjkiesch](https://www.ruby-forum.com/u/jjkiesch)\ **Post date:** [April 2, 2008, 7:46pm UTC](https://www.ruby-forum.com/t/looking-for-something-similar-to-in-groups-of-but-not-really/133700/2 "2008-04-02T19:46:39Z")
i found the transpose method which works unless i pass false to the options of in\_groups\_of. > > users.in\_groups\_of(3, false).transpose returns: IndexError: element size differs (2 should be 3) from (irb):19:in `transpose’ from (irb):19 from :0 are there any workarounds for this? ---
**Author:** ![jjkiesch](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/j/bc79bd/32.png) [@jjkiesch](https://www.ruby-forum.com/u/jjkiesch)\ **Post date:** [April 2, 2008, 8:01pm UTC](https://www.ruby-forum.com/t/looking-for-something-similar-to-in-groups-of-but-not-really/133700/3 "2008-04-02T20:01:51Z")
Hmm… maybe not quite that easy… that formula leaves some holes in the distribution of elements… ---
**Author:** ![jjkiesch](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/j/bc79bd/32.png) [@jjkiesch](https://www.ruby-forum.com/u/jjkiesch)\ **Post date:** [April 2, 2008, 7:48pm UTC](https://www.ruby-forum.com/t/looking-for-something-similar-to-in-groups-of-but-not-really/133700/4 "2008-04-02T19:48:44Z")
X in\_groups\_of Y = Z, and you want Z to be fixed… Assuming you know X (how big the array/collection is) and Z (the desired number of sub-arrays), the math is pretty simple. Something like: in\_groups\_of ((X/Z)+0.9999).to\_i or something like that ---
**Author:** ![jjkiesch](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/j/bc79bd/32.png) [@jjkiesch](https://www.ruby-forum.com/u/jjkiesch)\ **Post date:** [April 3, 2008, 3:39pm UTC](https://www.ruby-forum.com/t/looking-for-something-similar-to-in-groups-of-but-not-really/133700/5 "2008-04-03T15:39:33Z")
Josh K. wrote: > i’m trying to figure out an elegant way of taking an array or > enumerable object and dividing it as even as possible into sub arrays. Is your notion of “as even as possible” something like you want three sub-arrays to fill like this (where items are distributes as evenly as possible)? Item Count SubArrays 1 sa1 = [1] sa2 = [] sa3 = [] 2 sa1 = [1] sa2 = [2] sa3 = [] 3 sa1 = [1] sa2 = [2] sa3 = [3] 4 sa1 = [1,2] sa2 = [3] sa3 = [4] 5 sa1 = [1,2] sa2 = [3,4] sa3 = [5] 6 sa1 = [1,2] sa2 = [3,4] sa3 = [5,6] 7 sa1 = [1,2,3] sa2 = [4,5] sa3 = [6,7] 8 sa1 = [1,2,3] sa2 = [4,5,6] sa3 = [7,8] 9 sa1 = [1,2,3] sa2 = [4,5,6] sa3 = [7,8,9] 10 sa1 = [1,2,3,4] sa2 = [5,6,7] sa3 = [8,9,10] or as a dynamic number for in\_groups\_of would do? where g = (len/3).ceil array.len g SubArrays 1 1 sa1 = [1] sa2 = [] sa3 = [] 2 1 sa1 = [1] sa2 = [2] sa3 = [] 3 1 sa1 = [1] sa2 = [2] sa3 = [3] 4 2 sa1 = [1,2] sa2 = [3,4] sa3 = [] 5 2 sa1 = [1,2] sa2 = [3,4] sa3 = [5] 6 2 sa1 = [1,2] sa2 = [3,4] sa3 = [5,6] 7 3 sa1 = [1,2,3] sa2 = [4,5,6] sa3 = [7] 8 3 sa1 = [1,2,3] sa2 = [4,5,6] sa3 = [7,8] 9 3 sa1 = [1,2,3] sa2 = [4,5,6] sa3 = [7,8,9] 10 4 sa1 = [1,2,3,4] sa2 = [5,6,7,8] sa3 = [9,10] in\_groups\_of fills early rows rather than evenly distributing… note the ‘holes’ at 4, 7, 10, … that’s what prompted my last post yesterday ---
**Author:** ![jjkiesch](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/j/bc79bd/32.png) [@jjkiesch](https://www.ruby-forum.com/u/jjkiesch)\ **Post date:** [April 3, 2008, 5:48am UTC](https://www.ruby-forum.com/t/looking-for-something-similar-to-in-groups-of-but-not-really/133700/6 "2008-04-03T05:48:33Z")
Hey, assuming an arbitrary sized array (I chose 100 elements below) and you want to split it all up into at most 3 groups: x = (1…100).to\_a x.in\_groups\_of((x.length.to\_f / 3).ceil, false) HTH, Trevor On 4/2/08, Josh [removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid) wrote: > ``` > from (irb):19 > from :0 > > ``` > > are there any workarounds for this? > > > ## – Trevor S. [http://somethinglearned.com](http://somethinglearned.com) ---
**Author:** ![jjkiesch](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/j/bc79bd/32.png) [@jjkiesch](https://www.ruby-forum.com/u/jjkiesch)\ **Post date:** [April 3, 2008, 3:47pm UTC](https://www.ruby-forum.com/t/looking-for-something-similar-to-in-groups-of-but-not-really/133700/7 "2008-04-03T15:47:45Z")
You might want to check this out: [http://refactormycode.com/codes/167-split\_in\_groups-instead-of-in\_groups\_of](http://refactormycode.com/codes/167-split_in_groups-instead-of-in_groups_of) ---
**Author:** ![jjkiesch](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/j/bc79bd/32.png) [@jjkiesch](https://www.ruby-forum.com/u/jjkiesch)\ **Post date:** [April 3, 2008, 6:39pm UTC](https://www.ruby-forum.com/t/looking-for-something-similar-to-in-groups-of-but-not-really/133700/8 "2008-04-03T18:39:29Z")
exactly what i was looking for! thanks.