Re: split the sublists into parts according to some rules

*To*: mathgroup at smc.vnet.net*Subject*: [mg127947] Re: split the sublists into parts according to some rules*From*: Bob Hanlon <hanlonr357 at gmail.com>*Date*: Tue, 4 Sep 2012 05:47:46 -0400 (EDT)*Delivered-to*: l-mathgroup@mail-archive0.wolfram.com*Delivered-to*: l-mathgroup@wolfram.com*Delivered-to*: mathgroup-newout@smc.vnet.net*Delivered-to*: mathgroup-newsend@smc.vnet.net*References*: <20120903065630.0E5726897@smc.vnet.net>

To handle vectors splitToParts[list_?VectorQ, segments_Integer?Positive] := splitToParts[{list}, segments][[1]] /; segments <= Length[list] splitToParts[list_List, segments_Integer?Positive] := Module[{len, revList = Select[list, Length[#] >= segments &]}, (len = Floor[Length[#]/segments]; If[segments*len == Length[#], Partition[#, len], Join[{Take[#, len + 1]}, splitToParts[{Drop[#, len + 1]}, segments - 1][[1]]]]) & /@ revList] On Mon, Sep 3, 2012 at 2:56 AM, Dana DeLouis <dana01 at me.com> wrote: > Hi. I see you have an excellent solution. > I'm not sure, but would you want the function to work on a vector as well? > > splitToParts[{a,b,c,d,e,f,g},2] > {} > > This is not any better, but takes a different approach. > > If one had 12 items, and wanted to group them into 5 groups, the size of each group might be: > > k=IntegerPartitions[12,{5}] //Last > {3,3,2,2,2} > > We note that the first 2 items are 1 larger then rest, the count being.. > > Mod[12,5] > 2 > > For the right-side group, we adjust the starting position of Partition, and don't allow overhang of the right. > > > SplitToParts[list_List,n_Integer?Positive]:=Module[ > {v,Fx}, > > (* Custom Function *) > > Fx[v_List,x_Integer?Positive]:=Module[ > {k=Length[v], > left, > right}, > > If[x==1,Return[v]]; > If[x==k,Return[List/@v]]; > > {m,p}=QuotientRemainder[k,x]; > > If[p==0, > Partition[v,k/x], > (* Else *) > left = Partition[v,m+1][[;;p]]; > right = Partition[v,m,m,{-p,-1}][[p-x;;]]; > Join[left,right] > ] > ]; > > (* If it's a vector.. *) > If[Depth[list]==2, > If[Length[list]<n,Return[{}],Return[Fx[list,n]]]]; > > (* Else it's a list *) > > v=Select[list,Length[#]>=n&]; > If[Length[v]==0,Return[{}] ]; > Map[Fx[#,n]&,v] > ] > > > // End of Function ============ > > Some test data: > > v={{a,b,c,d,e},{x,y,z},{a1,a2,a3,a4}}; > > SplitToParts[v,3] > {{{a,b},{c,d},{e}}, {{x},{y},{z}}, {{a1,a2},{a3},{a4}}} > > SplitToParts[v,4] > {{{a,b},{c},{d},{e}}, {{a1},{a2},{a3},{a4}}} > > SplitToParts[v,5] > {{{a},{b},{c},{d},{e}}} > > SplitToParts[v,6] > {} > > > Appears to work with a vector: > > v={a,b,c,d,e}; > > SplitToParts[v,3] > {{a,b},{c,d},{e}} > > SplitToParts[v,4] > {{a,b},{c},{d},{e}} > > SplitToParts[v,6] > {} > > = = = = = = = = = = > HTH :>) > Dana DeLouis > Mac & Mathematica 8 > = = = = = = = = = = > > > > > On Friday, August 31, 2012 4:01:50 AM UTC-4, Joug Raw 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! > > >

**References**:**Re: split the sublists into parts according to some rules***From:*Dana DeLouis <dana01@me.com>