an unreported fix to union.m

[Juan Pablo Carbajal]

Hi,

The developer of this software (see commments)
http://journal.frontiersin.org/article/10.3389/fninf.2013.00008/abstract

fixed an compatibility issue in union.m of octave. Of course the fix
is not compatible with Octave standards. However if we need this fix I
will port it.

The difference is

--- /home/juanpi/Devel/octave/default/scripts/set/union.m
+++ /home/juanpi/Downloads/ndt.1.0.4_exported/octave_code/union.m
@@ -40,7 +40,7 @@
 ## @seealso{unique, intersect, setdiff, setxor, ismember}
 ## @end deftypefn

-## Author: jwe
+## Author: jwe, modified by Ethan Meyers 2015

 function [y, ia, ib] = union (a, b, varargin)

@@ -48,11 +48,35 @@
     print_usage ();
   endif

-  [a, b] = validsetargs ("union", a, b, varargin{:});
+

   by_rows = nargin == 3;
   isrowvec = isvector (a) && isvector (b) && isrow (a) && isrow (b);

+
+  % Modified by Ethan to deal with creating a union between an empty
vector and a cell array
+  if isempty(a)
+    if by_rows
+      y = unique(b, 'rows');
+    else
+      y = unique(b);
+    end
+    return
+  end
+
+ if isempty(b)
+    if by_rows
+      y = unique(a, 'rows');
+    else
+      y = unique(a);
+    end
+    return
+ end
+
+
+ [a, b] = validsetargs ("union", a, b, varargin{:});
+
+
   if (by_rows)
     y = [a; b];
   else


Comments?