Versión (10,8 KB) por Jan
Choose K elements from a vector with repetitions and order [MEX]
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Actualizado 1 ene 2010

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VChooseKRO(V, K) creates a matrix, which rows are all permutations created by choosing K elements of the vector V with order and with repetitions.

V: Array of class DOUBLE, SINGLE, (U)INT8/16/32/64, LOGICAL, CHAR.
Prefer (U)INT8 or (U)INT16 for speed.
K: Number of elements to choose.

Y: Matrix of size [NUMEL(V)^K, K].
Y has the same class as the input V.

Choose 2 elements from [1,2,3]:
VChooseKRO(1:3, 2) ==> [1,1; 1,2; 1,3; 2,1; 2,2; 2,3; 3,1; 3,2; 3,3]
For speed cast the input to integer types if possible:
Y = double(VChooseKRO(int16(1:1000), 2));
is faster than:
Y = VChooseKRO(1:1000, 2);
To get the permutations of cell arrays, permute the index:
C = {'a', 'b', 'c', 'd'};
C2 = C(VChooseKRO(1:4, 2))
==> C2 = {'a', 'b'; 'a', 'c'; 'a', 'd'; 'b', 'c'; 'b', 'd'; 'c', 'd'}

This MEX version is faster than NPERMUTEK and the more general COMBINATOR of Matt Fig: ~8 times for small arrays, ~2 times for (N=2000, K=2), ~10 times for (N=2, K=16, Class=INT8). COMBN of Jos is again slower than Matt's functions and it does not handle INT classes. See screen shot.

Tested: Matlab 6.5, 7.7, 7.8, WinXP, Compilers: BCC5.5, LCC2.4/3.8, Open Watcom 1.8
The unit-test TestVChooseKRO should be called after compiling. It compares the speed of VChooseKRO with COMBN, NPERMUTEK and COMBINATOR, if these files are found in the path.

See also: VChooseK (no repetitions, no order):

I'd appreciate suggestions for improvements and bug reports sent through email - thanks.

Citar como

Jan (2024). VChooseKRO (, MATLAB Central File Exchange. Recuperado .

Compatibilidad con la versión de MATLAB
Se creó con R2009a
Compatible con cualquier versión
Compatibilidad con las plataformas
Windows macOS Linux
Más información sobre Antennas, Microphones, and Sonar Transducers en Help Center y MATLAB Answers.

Inspirado por: permn, N_PERMUTE_K, COMBINATOR -combinations AND permutations

Inspiración para: VChooseKO

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