How do I swap 2 rows of a cell array?

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Pietro Fedrizzi
Pietro Fedrizzi on 21 Oct 2021
Commented: dpb on 21 Oct 2021
I have a 3x2 cell array and I need to swap row 2 and row 3. How can I solve this simple problem? Is there a function to do so that I don't know?

Accepted Answer

dpb
dpb on 21 Oct 2021
One way...
>> C=num2cell(randi(10,3,2))
C =
3×2 cell array
{[5]} {[1]}
{[9]} {[5]}
{[6]} {[5]}
>> C(2:3,:)=flipud(C(2:3,:))
C =
3×2 cell array
{[5]} {[1]}
{[6]} {[5]}
{[9]} {[5]}
>>
  7 Comments
Bruno Luong
Bruno Luong on 21 Oct 2021
"Change the indices to 2 and 4 (presuming at least four rows in the array, of course) and they don't do the same thing at all."
??? I just don't know what your are trying to say here. They do the same thing to my book
C=num2cell(randi(10,5,2))
C = 5×2 cell array
{[ 1]} {[6]} {[ 1]} {[4]} {[ 6]} {[2]} {[ 3]} {[8]} {[10]} {[4]}
Corg = C;
% dpb method
C([2 4],:)=flipud(C([2 4],:))
C = 5×2 cell array
{[ 1]} {[6]} {[ 3]} {[8]} {[ 6]} {[2]} {[ 1]} {[4]} {[10]} {[4]}
C=Corg;
% Bruno method
C([2 4],:)=C([4 2],:)
C = 5×2 cell array
{[ 1]} {[6]} {[ 3]} {[8]} {[ 6]} {[2]} {[ 1]} {[4]} {[10]} {[4]}
dpb
dpb on 21 Oct 2021
You wrote above
% dpb method
C([2 4],:)=flipud(C([2 4],:))
but that is NOT the code I wrote; you elided the colon that selects contiguous rows.
What I actually wrote in the original answer was
C([2:3],:)=flipud(C([2:3],:));
So, when change the 3 to a 4 one will get 3 rows instead of just two because I assumed (given the OP's example) there could be a more general case of wanting more than just two rows.
You just missed seeing the other colon, Bruno...

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More Answers (1)

Bruno Luong
Bruno Luong on 21 Oct 2021
C([2 3],:) = C([3 2],:);

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