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arraysmatlabmatrix
Jader Dias
Jader Dias

Reputation: 90475

How to obtain the mirror image of an array (MATLAB)?

Given an array:

array1 = [1 2 3];

I have to reverse it like so:

array1MirrorImage = [3 2 1];

So far I obtained this ugly solution:

array1MirrorImage = padarray(array1, [0 length(array1)], 'symmetric', 'pre');
array1MirrorImage = array1MirrorImage(1:length(array1));

Is there a prettier solution to this?

Upvotes: 21

Views: 58138

Answers (4)

Lorenzo Cabila
Lorenzo Cabila

Reputation: 1

Use that man:%to array's mirror r=input('insert rows');c=('insert columns')b=size(x); r=b(1);c=b(2); a=0; y(r,c)=0; for i=1:r n=0; g=r-a; a=a+1; for j=1:c n=n+1;d(i,j)=x(g,n); end end disp(y)

Upvotes: -1

gnovice
gnovice

Reputation: 125854

UPDATE: In newer versions of MATLAB (R2013b and after) it is preferred to use the function flip instead of flipdim, which has the same calling syntax:

a = flip(a, 1);  % Reverses elements in each column
a = flip(a, 2);  % Reverses elements in each row


Tomas has the right answer. To add just a little, you can also use the more general flipdim:

a = flipdim(a, 1);  % Flips the rows of a
a = flipdim(a, 2);  % Flips the columns of a

An additional little trick... if for whatever reason you have to flip BOTH dimensions of a 2-D array, you can either call flipdim twice:

a = flipdim(flipdim(a, 1), 2);

or call rot90:

a = rot90(a, 2);  % Rotates matrix by 180 degrees

Upvotes: 31

Tomas Aschan
Tomas Aschan

Reputation: 60574

you can use

rowreverse = fliplr(row) %  for a row vector    (or each row of a 2D array)
colreverse = flipud(col) % for a column vector (or each column of a 2D array)

genreverse = x(end:-1:1) % for the general case of a 1D vector (either row or column)

http://www.eng-tips.com/viewthread.cfm?qid=149926&page=5

Upvotes: 14

Scottie T
Scottie T

Reputation: 12195

Another simple solution is

b = a(end:-1:1);

You can use this on a particular dimension, too.

b = a(:,end:-1:1); % Flip the columns of a

Upvotes: 20

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