Replace arrays of a matrix with a vector

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amin
amin on 4 Feb 2020
Commented: amin on 4 Feb 2020
Hi,
I have a matrice R like :
R=zeros(3);
I need to change 3 array of R:
c=[1 1;3 2;1 2];
with new values in this vector:
Newvalue=[ 3 7 9];
So the final result is :
R=[3 9 0;0 0 0;0 7 0]
I know that I can do it easily with a For loop to check every element and replace new value.
But I want to vectorize this, i.e. with no loop.

Accepted Answer

KSSV
KSSV on 4 Feb 2020
Edited: KSSV on 4 Feb 2020
Read about sub2ind.
R=zeros(3);
c=[1 1;3 2;1 2];
Newvalue=[ 3 7 9];
% get global indices
idx = sub2ind(size(R),c(:,1),c(:,2)) ;
R(idx) = Newvalue
  1 Comment
amin
amin on 4 Feb 2020
Thank you so much, it is exacly what I was looking for.

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