How to extract a column from a matrix in Matlab and Octave

To extract a column of a matrix in Matlab and Octave, specify the column number (n) and colon (:) in place of the row number.

M(:,n)

This command extracts all the values of the nth column from the matrix.

Example

Define a matrix 2x3

X = [1 2 1 ; 3 1 1]

The matrix has two rows and three columns

1 2 1
3 1 1

To extract the first column, enter X(:,1)

X(:,1)

This command extracts the first column of the matrix

1
3

To extract the second column type X(:,2)

X(:,2)

This command extracts the second column of the matrix

2
1

To extract the third column type X(:,3)

X(:,3)

The command extracts the third column of the matrix

1
1