% FUNCTION [ x, e ] = LS_QR( A, b )
%
% Least square solution of an overdetermined system Ax = b
% where A  is  a M-by-N matrix with M > N
%       x  is  a M-by-1 vector
%       b  is  a M-by-1 vector
%
% This is done using QR decomposition of A.
% Also returned: e (scalar) the euclidian norm of Ax-b

function [ x, e ] = ls_qr( A, b )
  
  error( nargchk( 1, 2, nargin ) );
  
  M = size( A, 1 );
  N = size( A, 2 );
  
  [ Q, R ] = qr( A );
  
  U = R( 1:N, 1:N );
  
  c = Q' * b;
  
  d = c( 1:N );
  
  error( 'unfinished' );