1 files changed, 30 insertions, 0 deletions
diff --git a/xxpp_to_xpxp.m b/xxpp_to_xpxp.m
new file mode 100644
index 0000000..d6efbe9
--- /dev/null
+++ b/xxpp_to_xpxp.m
@@ -0,0 +1,30 @@
+function S_permuted = xxpp_to_xpxp(S)
+    % Permutes the entries of the input from xxpp ordering to xpxp ordering.
+    %
+    % Args:
+    %   S (array): input even dimensional square matrix or array
+    %
+    % Returns:
+    %   S_permuted (array): permuted matrix or array
+
+    shape = size(S);
+    n = shape(1);
+
+    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 length(shape) == 2
+        if shape(1) ~= shape(2)
+            error('The input matrix is not square');
+        end
+        S_permuted = S(ind, ind);
+    else
+        S_permuted = S(ind);
+    end
+end
+