X-Git-Url: http://gitweb.michael.orlitzky.com/?p=octave.git;a=blobdiff_plain;f=permutation_matrices.m;fp=permutation_matrices.m;h=9032d2e8eef5528355985d040133201a5421dea2;hp=0000000000000000000000000000000000000000;hb=23a3da45293aef5568409c8c1c46fc3b0758ca2d;hpb=8ca30867e869231f85848dc14e15f11e6d9c732b

diff --git a/permutation_matrices.m b/permutation_matrices.m
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+++ b/permutation_matrices.m
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+function PMs = permutation_matrices(integerN)
+  ## Generate all permutation matrices of size ``integerN``.
+  ##
+  ## INPUT:
+  ##
+  ##   - ``integerN`` -- The dimension of the resulting matrices.
+  ##
+  ## OUTPUT:
+  ##
+  ##   - ``PMs`` -- A cell array of permutation matrices.
+  ##
+
+  if (integerN < 1)
+    PMs = NA;
+    return;
+  end
+
+  ## Append to this as we generate them.
+  PMs = {};
+
+  ## Generate all permutations of [1,2,...,integerN].
+  permutations = perms([1:integerN]);
+
+  for idx = [ 1 : factorial(integerN) ]
+    sigma = permutations(idx,:);
+    ## Create a permutation matrix from the permutation, sigma.
+    P = eye(integerN) (sigma,:);
+    PMs{end+1} = P;
+  end
+
+end