function [y]=std_rows(x)
% standardise rows of x
%
 [m,n]=size(x);
 y=x-repmat(mean(x,2),1,n);

 v=std(y')'; i=find(v<=0); y(i,:)=0; v(i)=1; 
 y=y./repmat(v,1,n);
%