VChooseKRO 1.0

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.INPUT: 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.OUTPUT: Y: Matrix of size [NUMEL(V)^K, K]. Y has the same class as the input V.EXAMPLES: 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 1.8The 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): http://www.mathworks.com/matlabcentral/fileexchange/26190I'd appreciate suggestions for improvements and bug reports sent through email - thanks

Requirements:	No special requirements
Platforms:	Matlab
Keyword:	Classes,  Compilers,  Functions,  Handle,  Matlab,  Matt,  Screen,  Slower,  Tested,  Winxp
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