Create a diagonal matrix with a for loop from a vector
显示 更早的评论
I want to use the ML vector to create a diagonal matrix of only the values of the ML vector on the diagonal and make a new ML matrix with zeros everywhere else and the values of the ML vector along the diagonal of the new ML matrix. Essentially I am trying to write the code for diag(ML).
ML = rand([5 1])
for j = 1:length(ML)
for i = 1:j
if i < j
ML(i,j) == 0
elseif i > j
ML(i,j) == 0
else
ML(i,j) = ML(j)
end
end
end
采纳的回答
(If you are required to use a loop)
It is better to use another variable to get an output.
ML = rand([5 1])
Pre-allocate output matrix according to the size.
%Using max() in case ML is a row vector
Mout = zeros(max(size(ML)))
%You can also obtain the result without double for loop
for j = 1:numel(ML)
%Directly define the values
Mout(j,j)=ML(j);
end
Mout
更多回答（1 个）
Here are three way to define a diagonal in a square matrix of zeros that do not require a loop.
eye()
ML = rand([5 1])
Mout = eye(numel(ML)).*ML
Indexing with sub2ind
n = numel(ML);
Mout = zeros(n);
ind = sub2ind([n,n],1:n,1:n);
Mout(ind) = ML
Indexing without sub2ind
This shortcut works because we're working with a square matrix.
n = numel(ML);
Mout = zeros(n);
Mout(1:n+1:end) = ML
1 个评论
Dyuman Joshi
2023-4-1
I wonder if this is also the implementation in diag(input) or diag(input,0)
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