Assign the same variable to all elements of a Matrix

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Adil Bendouro
Adil Bendouro on 8 Nov 2021
Commented: Adil Bendouro on 9 Nov 2021
I would like to assign a variable to all elements of a Matrix without using a for loop to obtain a matrix M such that : M(nxn) = [x , x, x , x ,x ... ].
In my particular case x is an sdpvar and M is a matrix I use to set up the constraints of an optimisation problem.
Thank you

Answers (2)

Matt J
Matt J on 8 Nov 2021
I haven't worked with YALMIP, but can't you do
M=sdpvar(n);
M(:)=x;
  1 Comment
Adil Bendouro
Adil Bendouro on 8 Nov 2021
That is what I initially tried to do but it doesn't seem to work when the variables are multidimensional.
In my case I have:
M = sdpvar(10,10,10);
x = sdpvar(10,1);
M(:,:,:) = x;
which gives: In an assignment A(I) = B, the number of elements in B and I must be the same.

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John D'Errico
John D'Errico on 8 Nov 2021
As with Matt, I have not used the code, but this should work.
M = repmat(sdpvar(1,1),[10 10 10]);
  1 Comment
Adil Bendouro
Adil Bendouro on 9 Nov 2021
Unfortunately repmat didn't work for me. I believe that it is because it assigns copies of the variable x instead of the actual variable. Therefore the constraints of my linear program are not applied to x, which makes the optimisation problem unbounded.

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