Asked by ss
on 27 Dec 2012

Hi

if we have a matrix and we want to change the position of its array, rows and columns simultaneously, using two index vector B1 and B2, how can we use this command, i.e for instance u=[u11 u12 u13 u14;u21 u22 u23 u24;u31 u32 u33 u34;u41 u42 u43 u44]; B1=[1 4 3 2] B2=[3 2 1 4](B1 and B2 themselves are columns of a matrix) such that B1 is used for changing rows and B2 for changing columns, so u would be u=[u13 u12 u11 u14;u43 u42 u41 u44;u33 u32 u31 u34; u23 u22 u21 u24] thanks

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Answer by Jan Simon
on 27 Dec 2012

Edited by Jan Simon
on 27 Dec 2012

Accepted answer

You can simply use the index vectors to resort rows and columns:

u = [11 12 13 14; ... 21 22 23 24; ... 31 32 33 34; ... 41 42 43 44]; B1 = [1 4 3 2]; B2 = [3 2 1 4];

u = u(B1, B2);

>> u = 13 12 11 14 43 42 41 44 33 32 31 34 23 22 21 24

Answer by Azzi Abdelmalek
on 27 Dec 2012

Edited by Azzi Abdelmalek
on 27 Dec 2012

u=magic(4) % Example of u n=size(u,1) B1=randperm(n) % Example of B1 B2=randperm(n)' % Example of B2 u=u(:,B1) u=u(B2,:)

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