
Re: split the sublists into parts according to some rules
Posted:
Sep 3, 2012 3:00 AM


On Aug 31, 1:01 am, Joug Raw <joug...@gmail.com> wrote: > Dear all, > > I have a long list which has many sublists inside, > > Thelonglist={{a,b,c,d,e},{x,y,z},{a1,a2,a3,a4},...} > > Each sublist has length > 1(no single element sublist exists) . And the > lengths of the sublists are different and unknow in advanced. The length of > some of the sublists are odd number, such as {a,b,c,d,e} and {x,y,z}. Some > sublists have even number list length, like {a1,a2,a3,a4}. > > What I want to achieved is to split each sublist into two (or three, or > more) parts. In the two parts case, if the length of original sublist is > even number, the two new parts will have same length, e.g, {a1,a2,a3,a4} > become {{a1,a2},{a3,a4}}. If the sublist has length in odd number, > after splitting one of the two parts should have one more element than the > other. > > That is, > Input: Thelonglist={{a,b,c,d,e}, {x,y,z}, {a1,a2,a3,a4},...} > Output: Newlist={{a,b,c}, {d,e}}, {{x,y}, {z}}, {{a1,a2}, {a3,a4}},...} > > Or the same idea for the three parts case, > Input: Thelonglist={{a,b,c,d,e}, {x,y,z}, {a1,a2,a3,a4},...} > Output: Newlist={{{a,b}, {c,d}, {e}}, {{x},{y},{z}}, {{a1}, {a2}, > {a3,a4}}, ...} > > For the case of 4 parts, the number 4 is larger than the length of some > sublists and I will abandon those list with short length. > Input: Thelonglist={{a,b,c,d,e}, {x,y,z}, {a1,a2,a3,a4},...} > Output: Newlist={{{a}, {b}, {c}, {d,e}}, {{a1}, {a2}, {a3}, {a4}}, ...} > > Could there be a simple function to achieve this idea generally? Say, a > function like *SplittoPart[**list_*, *partnumber_**]*, in which I just need > to give the input list and the number of parts of sublists I want to have. > Then it will do the job above. If the number of sublist is larger then the > length of some sublists, the function just abandon those short list and do > the split(or partition) work on the other lists with long enough length. > Could some one help me on this? > > If that is too complicated, I would still be happy to see some one could > give me a solution only for the case of splitting to two parts, > > Input: Thelonglist={{a,b,c,d,e}, {x,y,z}, {a1,a2,a3,a4},...} > Output: Newlist={{a,b,c}, {d,e}}, {{x,y}, {z}}, {{a1,a2}, {a3,a4}},...} > > Thanks a lot for your kind help!
splitr[list_,r_] := subsplitr[#,r]&/@list/.{}>Sequence[]
subsplitr[sublist_,r_] := With[{n = Length@sublist}, If[n < r, {}, Take[sublist,#]& /@ (Transpose@{Most@#+1,Rest@#}&)[ FoldList[Plus,0,Floor[n/r]+Boole@Thread[Range@r<=Mod[n,r]]]]]]
longlist = {{a, b, c, d, e}, {x, y, z}, {a1, a2, a3, a4}};
splitr[longlist,2]
{{{a, b, c}, {d, e}}, {{x, y}, {z}}, {{a1, a2}, {a3, a4}}}
splitr[longlist,3]
{{{a, b}, {c, d}, {e}}, {{x}, {y}, {z}}, {{a1, a2}, {a3}, {a4}}}
splitr[longlist,4]
{{{a, b}, {c}, {d}, {e}}, {{a1}, {a2}, {a3}, {a4}}}

