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Re: split the sublists into parts according to some rules
*To*: mathgroup at smc.vnet.net
*Subject*: [mg127936] Re: split the sublists into parts according to some rules
*From*: Dana DeLouis <dana01 at me.com>
*Date*: Mon, 3 Sep 2012 02:56:30 -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
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!
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