How can I create one vector x to have this function correct? x has to be the column vector k- 'th of A, from its diagonal to the end

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Victoria Ródenas
Victoria Ródenas 2019-12-11
评论： Ridwan Alam 2019-12-11
function [Q, R] = miqr(A)
[nr,nc]=size(A);
Q=eye(nr);
k=A(:,1:nc-1);
x=k(2:nr,nc); --> the error is here, it says "index in position 2 exceeds array bounds(musn not exceed 4)
H=Householder(VecHh(x));
P=blkdiag(1,H);
A=P*A;
Q=P*Q;
R=A;
Q=Q';
end
okay, thank you so much, i dont know what value of x i am expecting, the only request for my exercise is that x has to be the column vector k- 'th of A, from its diagonal to the end
the excercise is create one random array and then apply the function something like this :
>> A=rand(5)
A =
0.8147 0.0975 0.1576 0.1419 0.6557
0.9058 0.2785 0.9706 0.4218 0.0357
0.1270 0.5469 0.9572 0.9157 0.8491
0.9134 0.9575 0.4854 0.7922 0.9340
0.6324 0.9649 0.8003 0.9595 0.6787
>> [Q, R] = miqr(A)
Index in position 2 exceeds array bounds (must not exceed 4).
Error in miqr (line 5)
x=k(2:nr,nc);
* but here is y error *
function A = Householder(v)
%% Householder matrix of base v
v = reshape(v,length(v),1); % v is now a column vector
A = eye(length(v)) - 2* v*v' /norm(v)^2;
end
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回答（1 个）

Ridwan Alam
Ridwan Alam 2019-12-11
k has size nr x (nc-1). you are trying to assign x = k(2:nr,nc) which means the nc-th column of k. but k doesn't have nc-th column, it has nc-1 columns.
Now for me to debug more, you need to let me know what H=Householder(VecHh(x)) is doing and what size and value of x are you expecting.

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