--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/m-toolbox/classes/+utils/@math/randelement.m	Wed Nov 23 19:22:13 2011 +0100
@@ -0,0 +1,54 @@
+% RANDELEMENT(VECTOR,J) returns J random samples chosen in the VECTOR array.
+%
+%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
+%
+% DESCRIPTION: RANDELEMENT(VECTOR,N) returns N random samples chosen in the
+%                                    VECTOR array. If VECTOR is a scalar,
+%                                    than it answers with N samples from
+%                                    1:1:VECTOR.
+%
+% CALL:       out = randelement(arr, j)
+%
+% INPUTS:     arr - numerical vector array or cell vector array; can be
+%                   single line or single column.
+%             j   - number of samples to extract
+%
+% OUTPUTS:    out - numerical vector array or cell vector array, shaped as
+%                   the input 'arr', containing j elements chosen among 
+%                   those included in 'arr'.
+%
+% VERSION: $Id: randelement.m,v 1.5 2009/08/10 00:49:50 nicola Exp $
+%
+% HISTORY: 06-02-2008 N Tateo
+%             Creation
+%
+%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
+
+function out = randelement(arr, j)
+  
+   if nargin < 2
+      error('randelement:tooFewInputs','The randelement function requires two input arguments.');
+   elseif ~isa(arr,'double') && ~isa(arr,'cell')
+      error('randelement:wrongInput','The input to the randelement function must be a numerical or cell array.')
+   elseif ~isvector(arr)
+      error('randelement:wrongShape','The input to the randelement function must be a vector.')
+   end
+   
+   N = length(arr);
+   if N==1
+       if iscell(arr), arr = num2cell([1:1:arr{1}]);
+       else arr = [1:1:arr];
+       end
+       N = length(arr);
+   end
+   out = arr(randi(N,1,j));
+  
+   if size(arr,1)==1 % reshape as a row vector
+      out = reshape(out,1,[]);
+   else              % reshape as a column vector
+      out = reshape(out,[],1);
+   end
+  
+end
+% END
+