--- setdiff.m.old	2006-05-01 08:28:29.000000000 -0400
+++ setdiff.m	2006-05-01 08:53:14.000000000 -0400
@@ -28,12 +28,23 @@
 ## Author: Paul Kienzle
 ## Adapted-by: jwe
 
-function c = setdiff (a, b)
+function c = setdiff (a, b, byrows)
 
-  if (nargin != 2)
-    usage ("setdiff (a, b)");
+  if (nargin < 2)
+    usage ("setdiff (a, b) or setdiff (a, b, 'rows')");
   endif
 
+  if (nargin > 2)
+    if (isempty (strmatch (byrows, "rows", "exact")))
+      error("Third input can only be 'rows'");
+    else
+      byrows = 1;
+    endif
+  else
+    byrows = 0;
+  endif
+
+  if (byrows == 0)
   c = unique (a);
   if (! isempty (c) && ! isempty (b))
     ## Form a and b into combined set.
@@ -47,6 +58,24 @@
       c = c.';
     endif
   endif
+  endif ## if (byrows == 0)
 
+  if (byrows == 1)
+    c = unique (a, "rows");
+    if (! isempty (c) && ! isempty (b))
+      ## Form a and b into combined set.
+      b = unique (b, "rows");
+      [dummy, idx] = sortrows ([c; b]);
+      ## Eliminate those elements of a that are the same as in b.
+      n = length (dummy);
+      c(idx(find (dummy(1:n-1) == dummy(2:n))), :) = [];
+    endif
+  endif
+  
 endfunction
   
+%!assert(setdiff(["bb";"zz";"bb";"zz"],["bb";"cc";"bb"],"rows"), "zz")
+%!assert(setdiff(["b";"z";"b";"z"],["b";"c";"b"],"rows"), "z")
+%!assert(setdiff(["b";"z";"b";"z"],["b";"c";"b"]), "z")
+%!assert(setdiff([1, 1; 2, 2; 3, 3; 4, 4], [1, 1; 2, 2; 4, 4], "rows"), [3 3])
+%!assert(setdiff([1; 2; 3; 4], [1; 2; 4], "rows"), 3)