# Swapping the columns based on matrix even length

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Venkat Ta on 18 Sep 2019
Commented: madhan ravi on 18 Sep 2019
Is there any pre-function in Matlab to change the column order below like it?
Original column orders = 1 2 3 4 5 6 7 8 9 10
Modified coulmn orders = 2 1 4 3 6 5 8 7 10 9
cell format and matrix format how can it change?
Thanks

Johannes Fischer on 18 Sep 2019
Edited: Johannes Fischer on 18 Sep 2019
Assuming that there is always an even number of columns:
matrix = repmat(1:10, [3, 1]);
L = size(matrix, 2);
ind = [2:2:L; 1:2:L];
matrix_reorderedColumns = matrix(:, ind(:))

madhan ravi on 18 Sep 2019
Edited: madhan ravi on 18 Sep 2019
No matter odd or even:
ix=(2:2:size(matrix,2)) + [0;-1];
% if > 2016b ix = bsxfun(@plus, 2:2:size(a,2), [0;-1])
Wanted = matrix(:,[ix(:);end.*(mod(end,2)~=0)])

Rik on 18 Sep 2019
Or with a few small tweaks:
N=10;%set to something odd or even to check both
matrix = repmat(1:N, [3, 1]);
ix=(2:2:(size(matrix,2)+1)) + [0;-1];
% if > 2016b ix = bsxfun(@plus, 2:2:size(a,2), [0;-1])
Wanted = matrix(:,ix(ismember(ix,1:size(matrix,2))))
madhan ravi on 18 Sep 2019
Thanks Rik :) !