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Questions on the manipulation of List objects in Mathematica, and the functions used for these manipulations.
9
votes
Pure function of lists
Remove@f
f[s_,l_]:= Evaluate@Total[Sign[s] Slot/@Abs@s]& @@@l
6
votes
4
answers
182
views
Check if list is singleton in sub linear time
A singleton is a list whose elements are equal. Some ways of checking this in Mathematica:
{Equal@@#&,
1==Length@Union@#&,
MatchQ[#,{x_ ..}]&}
I started benchmarking:
Table[First@RepeatedTiming[#@ …
5
votes
How to generate Venn diagram from a universe and 3 random sets?
the 'math' code
Remove[universe,a,b,c,onlya,onlyb,onlyc,onlyab,onlybc,onlyca,onlyabc]
universe = Range[1, 50];
a = RandomSample[#, RandomInteger@{1, Length@#}]\
&[universe ⋂ Range[3, 30]];
b = Rando …
5
votes
3
answers
246
views
Thread Matrices, like image channels
The code
With[{matA=Partition[Alphabet[],5],matB=Partition[Range@25,5]},
(* matA and matB are 5x5 matrices*)
MapThread[List,{matA,matB},2]
]
is fairly straightforward. The MapThread part does 'int …
3
votes
Successive chunking of a list
I'll just answer your first bullet point.
Evaluation code:
eval[func_]:=
ReleaseHold[Hold@func/.{
f -> (TakeLargest[#, UpTo@4] &),
list -> {19,4,12,1,17,13,7,14,10,11,6,18,20,15,16,3,8,5,2,9}}
]
…
2
votes
ArrayReshape in an almost rectangular way
Alright I don't know how to make nice looking plots yet
but kglr's approach
Transpose[{#[[All, {1, 2}]], #[[All, {3, 4}]], #[[All, 5]]}] &@list
and lecicr's first approach that calls RandomReal thre …
2
votes
Counting number of points in fluctuating lines that fall within a circle
Perhaps the cleanest way to find this distribution is with Nearest. I.e.
pts=RandomReal[{-10,10},{10000000,2}];
center={1,1};
rad=1;
Timing@Length@Nearest[pts,center,{\[Infinity],rad}]
(* .08 seconds …
1
vote
2
answers
99
views
ArrayReshape in an almost rectangular way
I want to make a list of many (say 1000) test instances for a geometry problem. The problem involves two line segments and a point. So I need
{
(* first line *) (*second line*) (*point*)
…
0
votes
Check if list is singleton in sub linear time
The compeditors:
adam0[l_List]:=Equal@@l;
adam1[l_List]:=1==Length@Union@l;
adam2[l_List]:=MatchQ[l,{x_ ..}];
adam3[l_List]:=If[Null===Do[If[l[[i]]==l[[i+1]],Return@0],{i,Length@l-1}],True,False];
all …