function h = r8mat_house_pre ( n, a, row, col )
%*****************************************************************************80
%
%% r8mat_house_pre() computes a Householder pre-multiplier matrix.
%
% Discussion:
%
% H(ROW,COL) has the property that the COL-th column of
% H(ROW,COL)*A is zero from entry ROW+1 to the end.
%
% In the most common case, where a QR factorization is being computed,
% ROW = COL.
%
% Licensing:
%
% This code is distributed under the GNU LGPL license.
%
% Modified:
%
% 17 April 2013
%
% Author:
%
% John Burkardt
%
% Input:
%
% integer N, the order of the matrices.
%
% real A(N,N), the matrix whose Householder matrix
% is to be computed.
%
% integer ROW, COL, specify the location of the
% entry of the matrix A which is to be preserved. The entries in
% the same column, but higher rows, will be zeroed out if A is
% premultiplied by H.
%
% Output:
%
% real H(N,N), the Householder matrix.
%
%
% Set up the vector V.
%
a_col(1:row-1,1) = 0.0;
a_col(row:n,1) = a(row:n,col);
v = r8vec_house_column ( n, a_col, row );
%
% Form the matrix H(V).
%
h = r8mat_house_form ( n, v );
return
end