CODEWITHSUNDEEP
arraysmatlabmatrix
System
System

Reputation: 241

How to move rows and columns of certain indices to either end of matrix?

I have a matrix let it be

A = 100x100 matrix

and a vector

B = [ 2 7 23 45 55 67 79 88 92]

And I want to bring these rows and columns to the end of the array meaning the last 9x9 block in A to be the rows and columns of B. (the last row of A should now be row 92 and the last column should be column 92)

Any ideas?

Upvotes: 2

Views: 628

Answers (3)

Santhan Salai
Santhan Salai

Reputation: 3898

One approach using ismember

B = [ 2 7 23 45 55 67 79 88 92];
oldIdx = 1:100;
newIdx = [oldIdx(~ismember(oldIdx,B)),B];
out = A(newIdx,newIdx);

Upvotes: 1

Robert Seifert
Robert Seifert

Reputation: 25232

One option with setxor:

A = reshape(1:10000,100,100);     %// matrix with linear indices
B = [ 2 7 23 45 55 67 79 88 92];  %// rows and cols to move to the end

idx = [setxor(1:size(A,1),B) B];  %// index vector for rows and cols
out = A(idx,idx)

For the simpler test case of B = [ 1 2 3 4 5 6 7 8 9 ]; you get:

enter image description here

Upvotes: 1

Shai
Shai

Reputation: 114796

Assuming you do not want to change the order of the rest of the rows/columns, let's start with arranging all the indices:

n = size(A,1);
allIdx = 1:n;
allIdx(B) = []; %// discard B from their original place
allIdx = [allIdx, B]; %// put B at the end
newA = A(allIdx, allIdx); %// Ta-DA!

Upvotes: 3

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