initial release

1 files changed, 32 insertions, 0 deletions

diff --git a/xpxp_to_xxpp.m b/xpxp_to_xxpp.m
new file mode 100644
index 0000000..fc732e2
--- /dev/null
+++ b/xpxp_to_xxpp.m
@@ -0,0 +1,32 @@
+function S_permuted = xpxp_to_xxpp(S)
+    % Permutes the entries of the input from xpxp ordering to xxpp ordering.
+    %
+    % Args:
+    %   S (array): input even dimensional square matrix or a row vector
+    %
+    % Returns:
+    %   S_permuted (array): permuted matrix or vector
+
+    shape = size(S);
+    if length(shape) > 2
+        error('The input matrix is not 2 dimensional');
+    end
+
+    n = shape(2);
+
+    if mod(n, 2) ~= 0
+        error('The input array is not even-dimensional');
+    end
+
+    n = n / 2;
+    ind = reshape(1:2*n, 2, [])';
+    ind = ind(:)';
+
+    
+    if shape(1) == shape(2)
+        S_permuted = S(ind, ind);
+    else
+        S_permuted = S(ind);
+    end
+end
+