How do I produce all possible permutations of a vector, selecting a chosen number of elements?

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aweller3 2021-11-26

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评论： Matt J 2021-11-28

Given some vector like a=[0:3] (but it doesn't have to be evenly spaced) I want to list all permutations (not combinations). I know perms can do this but it doesn't let you choose the number of elements you want.

I managed to do this choosing only 3 elements at a time using meshgrid. Here is my code for that:

%written in Octave

function C3 = ThreeNoteChordGen ()

%stores pitch classes 0 to 11

n=[0:11];

%initialize C3 as blank array;

C3=[];

[xx,yy,zz]=meshgrid(n,n,n);

[numRows, numCols, numPages] = size(zz);

for (countPage=1:numPages)

for (countCol=1:numCols)

newSegment=[zz(:,countCol,countPage), xx(:,countCol,countPage),yy(:,countCol,countPage)];

C3=[C3; newSegment];

endfor

endfunction

I'm having trouble adapting this method for choosing more elements at a time. I would appreciate any help. I'm very much a beginner programmer so I would rather you point me in the right direction rather than coding it for me (I probably won't understand your code);

Thank you

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Jeff Miller 2021-11-26

Check the answers here, especially the fileexchange function npermutek mentioned at the end.

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Answer 1

Matt J 2021-11-27

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编辑：Matt J 2021-11-27

在 MATLAB Online 中打开

a=[4,17,13,5,1,90];
n=3;
P=perms(1:n).';
b=nchoosek(a,n).' ;
out=reshape( b(P(:),:),n,[]).'
out = 120×3
    13    17     4
    13     4    17
    17    13     4
    17     4    13
     4    13    17
     4    17    13
     5    17     4
     5     4    17
    17     5     4
    17     4     5

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aweller3 2021-11-27

Both of the solutions from Matt J and Jeff Miller work perfectly for that. Thank you. Is it possible to allow duplicates like [0 0 0;0 0 1;0 1 0]?

Matt J 2021-11-28

Nothing in my solution forbids duplicates.

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How do I produce all possible permutations of a vector, selecting a chosen number of elements?

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