Householder Algorithm finding Q

31 ビュー (過去 30 日間)
Frederick Melanson
Frederick Melanson 2021 年 3 月 8 日
回答済み: Athul Prakash 2021 年 3 月 12 日
Hi, i have this algorithm:
function [Q,R] = householder(A)
% Write your code here.
[m,n]=size(A);
Q=eye(m);
for k=1:n
z = -sign(A(k,k))*norm(A(k:m,k));
v = [zeros(k-1,1); A(k,k)-z; A(k+1:m,k)];
f = v'*v;
if f == 0, continue; end
for j = k:n
c = v'*A(:,j);
A(:,j) = A(:,j)-(2*c/f)*v;
end
end
R=A;
end
I get the correct R matrix, but I can't seem to find Q correctly. Please let me know ASAP
  2 件のコメント
Frederick Melanson
Frederick Melanson 2021 年 3 月 9 日
I added an extra forloop at the end like this:
for j=k:m
c = v'*Q(:,j);
Q(:,j) = Q(:,j)-(2*c/f)*v;
end
Q=Q';
I get the lower triangular part of Q correctly, the problem is with the upper half of the matrix

サインインしてコメントする。

回答 (1 件)

Athul Prakash
Athul Prakash 2021 年 3 月 12 日
Hi Frederick,
You may prefer the MATLAB built-in qr() function.
[Q,R] = qr(M);
See this documentation:
Alternately, you may search the Mathworks File Exchange for alternate implementations of Householder algorithm. For example:
These are submissions by other MATLAB users, and not part of the MATLAB product. It is not tested or qualified by Mathworks, so use at your own responsibility.

カテゴリ

Find more on QSP, PKPD, and Systems Biology in Help Center and File Exchange

Community Treasure Hunt

Find the treasures in MATLAB Central and discover how the community can help you!

Start Hunting!

Translated by