diff --git a/nonunique.m b/nonunique.m
new file mode 100644
index 0000000000000000000000000000000000000000..cda8d85885cc94a9b66cb3e12e2be95a6fb858b4
--- /dev/null
+++ b/nonunique.m
@@ -0,0 +1,6 @@
+function [dupes, ind] = nonunique(A)
+[~, i, ~] = unique(A,'first');
+dupes = A(not(ismember(1:numel(A),i)));
+ind=ismember(A,dupes);
+end
+