CODEWITHSUNDEEP
arraysmatlabcombinationscombinatorics
Shahgee
Shahgee

Reputation: 3405

find possible combinations with specific condition

I want to calculate all possible combinations of 1:16 with 10 subsets.

combos = combntns(1:16,10)

But the condition is that the returned combos should have minimum 1 member of the following vectors:

V1=1:4,V2=5:8,V3=9:12,V4=13:16,

Any solution?

Upvotes: 0

Views: 109

Answers (1)

Luis Mendo
Luis Mendo

Reputation: 112749

With that problem size you can afford to generate all combinations and then select those that meet the requirements:

n = 16;  %// number of elements to choose from
c = 10;  %// combination size
s = 4;   %// size of each group (size of V1, V2 etc)

combos = nchoosek(1:n, c); 
ind = all(any(any(bsxfun(@eq, combos, reshape(1:n, 1,1,s,[])),2),3),4);
combos = combos(ind,:);

This can be generalized for generic elements and arbitrary condition vectors, assuming all vectors are the same size:

elements = 1:16;                    %// elements to choose from
c = 10;                             %// combination size
vectors = {1:4, 5:8, 9:12, 13:16};  %// cell array of vectors

s = numel(vectors{1});
combos = nchoosek(elements, c); 
ind = all(any(any(bsxfun(@eq, combos, reshape(cat(1,vectors{:}).', 1,1,s,[])),2),3),4); %'
combos = combos(ind,:);

Upvotes: 2

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