function [Y,STDD]=normvar(X)
%NORMVAR Normalize the variance in the columns of a matrix
% NORMVAR(X) normalizes the variance in the columns of the matrix X
% by dividing each column by its standard deviation.
%
% [Y,Z]=NORMVAR(X) returns the normalized matrix in Y and the 
% standard deviations of the columns of the matrix X in Z.
[M,N]=size(X); 
STDD=std(X);
if any(STDD<eps)
   Y=[];STDD=[];
   error('STD==0; divide-by-0 in NORMVAR')
end
STD=ones(size((1:M)'))*STDD;
Y=X./STD;
if nargout==1,STDD=[];,end