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function R = gqr3 (A)
%GQR3 QR factorization, based on Givens rotations
%
% Example:
% R = gqr3 (A)
% See also: testall
% Copyright 2006-2007, Timothy A. Davis.
% http://www.cise.ufl.edu/research/sparse
[m n] = size (A) ;
% parent = cs_etree (sparse (A), 'col') ;
for i = 2:m
% i
for k = 1:min(i-1,n)
% k
% Givens rotation to zero out A(i,k) using A(k,k)
G = givens2 (A(k,k), A(i,k)) ;
A ([k i],k:n) = G * A ([k i],k:n) ;
A (i,k) = 0 ;
% fprintf ('A(21,25)=%g\n', A(21,25)) ;
% if (A(21,25) ~= 0)
% pause
% end
end
end
R = A ;
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