PERMPOS

permpos(M, N) where M and N are non-negative integers produces a
logical (N!/M!(N-M)!)-by-N matrix in which each row contains a unique
permutation of M trues and (N-M) falses.

W = permpos(V, N) where V is an array with M elements a matrix W
where each row a contains the values of V in preserved order, but
uniquely permuted at the N columns. The remaining positions are set to
NaN. W = permpos(V, N, F) uses the value F rather than NaN.

[W, B] = permpos(V, ...) also returns the logical matrix B, which is
true for the positions that are filled by elements of V. Note that B
equals "permpos(numel(V),N)".

V can be a numerical array, a cell array of chars or a string
array. F (optional) should be of the same class as V.

Examples:
permpos(2, 4)
% -> [ 1 1 0 0
% 1 0 1 0
% 1 0 0 1
% 0 1 1 0
% 0 1 0 1
% 0 0 1 1 ]

permpos(1:2:3, 4) % ->
% -> [ 1 2 3 NaN
% 1 2 NaN 3
% 1 NaN 3 3
% NaN 1 2 3 ]

permpos({'a','b'}, 3, 'XX') % filler
% -> { 'a' 'b' 'XX' ; 'a' 'XX' 'b' ; 'XX' 'a' 'b'}

See also nchoosek, perms, randperm, true, false
On the file Exchange:
permn, PERMNK, permsk, allcomb, ballatsq, nones, nextpermpos