Is there any way to assign a value to the diagonals of a matrix (not just the main diagonal)?
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I have a vector of values that I want to assign to the diagonals of a matrix. So for example, if my vector is
v = [ 2 7 8 9 5];
I want to make a matrix to have all the elements of the 1st diagonal equal to v(1), all the elements of the second diagonal equal to v(2), all of the elements of the third (and main) diagonal equal to v(8), and so on.
Is there any way to do that?
2 Comments
Danilo NASCIMENTO
on 19 Feb 2014
Edited: Danilo NASCIMENTO
on 19 Feb 2014
Let me understand... The order of your matrix should the length of your v vector... Is that what you mean? Actually I don't know what are you trying to perform... But this way you will not fill the matrix completely, the extremes of the inverse main diagonal will be left blank.
Accepted Answer
Star Strider
on 19 Feb 2014
Edited: Star Strider
on 19 Feb 2014
There is no ‘ v(8) ’. I assume you mean v(3) = 8.
This looks so kludgy that I’m almost ashamed to post it, but if I understand your question, it does what you want:
v = [ 2 7 8 9 5]
vc = size(v,2);
M = zeros(round(vc/2));
for k1 = 1:vc
rvc2 = round(vc/2);
if k1 <= rvc2
Mi = diag(ones(1,k1)*v(k1), rvc2-k1);
elseif k1 > rvc2
Mi = diag(ones(1,abs(rvc2+1-round(k1/2)))*v(k1), rvc2-k1);
end
M = M + Mi;
end
The matrix it produces is:
M =
8.0000e+000 7.0000e+000 2.0000e+000
9.0000e+000 8.0000e+000 7.0000e+000
5.0000e+000 9.0000e+000 8.0000e+000
More Answers (2)
mohammed
on 19 Feb 2014
Dear Alex
v = [ 2 7 8 9 5];
for i = 1:length(v)
b{i} = eye(3)*v(i)% 3 is the size of identity Matrix
end
i hope it will help you.
Roger Stafford
on 20 Feb 2014
It depends on which side you call the "first" diagonal. If you use the order sense of matlab's 'diag' function, the diagonal numbers increase from lower left to upper right, so the first diagonal would be on the lower left. With definition do:
M = toeplitz(v(3:-1:1),v(3:5));
If you order them in the opposite direction, do:
M = toeplitz(v(3:5),v(3:-1:1));
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