bug fix for empty vector

entropy.m

@@ -17,6 +17,9 @@ function e=entropy(x)
 % $Revision$
 %
 % $Log$
+% Revision 2.3  2009/03/24 08:32:09  marwan
+% copyright address changed
+%
 % Revision 2.2  2005/04/06 12:58:08  marwan
 % changed from log2 to natural log
 %
@@ -32,8 +35,13 @@ function e=entropy(x)
 error(nargchk(1,1,nargin));
 if nargout>1, error('Too many output arguments'), end
 
-for j=1:size(x,2);
-  x(:,j)=x(:,j)./sum(x(:,j));
-  x2=x(find(x(:,j)),j);
-  e(:,j)=sum(-x2.*log(x2));
+if isempty(x)
+    e = 0;
+else
+    for j=1:size(x,2);
+      x(:,j)=x(:,j)./sum(x(:,j));
+      x2=x(find(x(:,j)),j);
+      e(:,j)=sum(-x2.*log(x2));
+    end
 end
+