Flipping a matrix in Matlab

Matlab and Octave both provide functions to flip matrices with ease.

To flip a matrix horizontally, mirroring it along the y-axis (from right to left), I use the fliplr() function:

fliplr(matrix)

For a vertical flip along the x-axis (from bottom to top), the flipud() function is ideal:

flipud(matrix)

Example

Let's walk through a practical example.

To start, I'll define a matrix and assign it to a variable:

M = [1,2;3,4]

This matrix is 2x2:

$$ M = \begin{pmatrix} 1 & 2 \\ 3 & 4 \end{pmatrix} $$

To reverse the columns in M, I simply use the fliplr(M) command:

M2 = fliplr(M)

This gives a new matrix, M2, where M has been flipped horizontally, with columns reversed:

$$ M2 = \begin{pmatrix} 2 & 1 \\ 4 & 3 \end{pmatrix} $$

Similarly, to reverse the row order in M, I can use the flipud(M) function, which flips the matrix vertically:

M3 = flipud(M)

Now, M3 is the vertically flipped version of M, with rows reordered from bottom to top:

$$ M3 = \begin{pmatrix} 3 & 4 \\ 1 & 2 \end{pmatrix} $$