function y=shiftl(x)
% shiftl - shift a column vector up one
% maintaining original length
% eg [ 1 2 3 4 ] --> [ 2 3 4 0]
if isvector(x)
	y = [ x(2:length(x)); 0];
else
	y = [ x(:,2:size(x,2)), zeros(size(x,1),1) ];
end
