[GAP Forum] labels in xgap

[William DeMeo]

That's great, it works.  Thank you!  -William

On Tue, Mar 22, 2011 at 3:37 PM, Russ Woodroofe <rsw9 at cornell.edu> wrote:
>
>
>        Dear William,
>        Here's a short sample, which relabels an inserted Sylow 2-subgroup of S_4 as P_2:
>
> G:=SymmetricGroup(4);
> Sym( [ 1 .. 4 ] )
>
> L:=GraphicSubgroupLattice(G);
> <graphic subgroup lattice "GraphicSubgroupLattice">
>
> H:=SylowSubgroup(G,2);
> Group([ (1,2), (3,4), (1,3)(2,4) ])
>
> ret:=InsertVertex(L, H);
> [ <vertex of graphic graph, label: "2", Serial:6>, true ]
>
> Relabel(L, ret[1], "P_2");
>
>        I think you should be able to work this around to your own situation.
>
>        The subgroup lattice library seems to internally use Relabel to label the vertices, and I don't see it pulling information from the subgroup itself -- though I didn't look terribly carefully.  But the above sample should make relabeling things under program control not too inconvenient...
>
>        Sincerely,
>
>                                                --Russ Woodroofe
>
> PS:  If you're using a Mac, let me recommend my native "Gap.app" front-end, which is a workalike for xgap.  Available at
> http://cocoagap.sourceforge.net/
>
>
> On Mar 22, 2011, at 4:52 PM, William DeMeo wrote:
>
>> Dear Forum,
>>
>> Is it possible to change the labels of vertices in a subgroup lattice
>> drawn by XGAP using the command line (rather than using "Change
>> Labels" in the "Poset" menu)?
>>
>> Here's an example:
>>
>> L:=GraphicSubgroupLattice(G1xG2);
>>
>> InsertVertex(L, HxK);
>> # insert here some command to change vertex label to "HxK"
>>
>> InsertVertex(L, HxG2);
>> # insert here some command to change vertex label to "HxG2"
>>
>> InsertVertex(L, G1xK);
>> # insert here some command to change vertex label to "G1xK"
>>
>> intsubs:=IntermediateSubgroups(G1xG2, HxK);
>> for j in [1..Size(intsubs.subgroups)] do
>>   InsertVertex(L,intsubs.subgroups[j]);
>> od;
>>
>> After I execute the loop, it's hard to tell what's what unless I have
>> already changed some labels with names like "HxK", "HxG2", etc. before
>> the loop.  Using the menu to do this each time is a bit tedious.
>>
>> (Also, it would be nice if I could use some stored list of short names
>> -- maybe acquired from StructureDescription -- to insert labels inside
>> the loop as well, but maybe that's asking too much... and perhaps such
>> a labelling would be even harder to interpret than the default number
>> labels; e.g. when the names are not unique.)
>>
>> Thanks in advance for any tips!
>>
>> -William
>>
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>
>