# Circulant Matrix [Column Wise Traversal]

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Tarek Hajj Shehadi on 18 Sep 2020
Commented: Rena Berman on 8 Oct 2020 at 15:46
Below is the row wise circulant matrix algorithm :
function C= circulant(x)
n=length(x);
C=zeros(n,n);
C(1,:)=x;
for i=2:n
C(i, :)=[C(i-1, n) C(i-1, 1:n-1)];
end
How can I compute the circulant matrix column wise based on what I wrote for the circulant matrix computed row wise?

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Rik on 20 Sep 2020
Circulant Matrix [Column Wise Traversal]
Below is the row wise circulant matrix algorithm :
function C= circulant(x)
n=length(x);
C=zeros(n,n);
C(1,:)=x;
for i=2:n
C(i, :)=[C(i-1, n) C(i-1, 1:n-1)];
end
How can I compute the circulant matrix column wise based on what I wrote for the circulant matrix computed row wise?
Rik on 20 Sep 2020
Tarek, removing you question and comments is very rude. I have restored some of your posts from the cache that Google creates. Why did you remove it? Are you afraid to be caught cheating? There is a reason you can't delete a question once you get an answer: people put in time to understand your problem, find a solution, and post it. The curteous thing to is to leave it up so future people with a similar problem can benefit from that time investment as well.
Rena Berman on 8 Oct 2020 at 15:46

Bruno Luong on 19 Sep 2020
function C= circulant(x)
n=length(x);
C=zeros(n,n);
C(:,1)=x;
for j=2:n
C(:,j)=[C(n,j-1); C(1:n-1,j-1)];
end

#### 1 Comment

Rik on 20 Sep 2020
Deleted comment by by Tarek Hajj Shehadi:
I have accepted your answer as it is the one I am looking for, I would also like to thank Matt J for also putting an effort in helping me. As for your answer its entirley what I was looking for just that I added C=C'; to transpose this matrix as required.

Matt J on 18 Sep 2020
function C= circulant(x)
n=length(x);
C=zeros(n,n);
C(1,:)=x;
for i=2:n
C(i, :)=[C(i-1, n) C(i-1, 1:n-1)];
end
C=C.';

#### 1 Comment

Rik on 20 Sep 2020
Deleted comment by by Tarek Hajj Shehadi:
Hello, The thing I was trying to make columnwise computation and the rowwise computation of the circulant matrix output the same matrix where in both cases, the entries are in same position so the problem I am encountering is perhaps in the for loop.

Bruno Luong on 18 Sep 2020
function C= circulant(x)
toeplitz(x,circshift(flip(x),1))
end

#### 1 Comment

Rik on 20 Sep 2020
Deleted comment by by Tarek Hajj Shehadi:
I wish to write the algorithm using for loops and not use the builtin function.

Bruno Luong on 19 Sep 2020
function C= circulant(x)
n = length(x);
C = x(mod((1:n)'-(1:n),n)+1);