How to use unique in an mxn matrix without sorting the columns?

For my project I have to account for any duplicate columns and remove them, but the original order of the columns must be retained. If I use the method below, the columns in the output get sorted. Is there a way to remove the duplicate columns in a matrix without sorting them?

I have a 2 by 4 matrix A:

A = [7, 2, 1, 9; 3, 2, 9, 11]

a_transpose = A.'

a_no_duplicate = unique(a_transpose, 'rows').'

After running the code, this is the output:

a_no_duplicate =

1 2 7 9

9 2 3 11

(Here the columns are sorted)

Answer 1

[Matt J]

A = [7, 2, 1, 1; 3, 2, 9, 9]

A = 2×4

7 2 1 1 3 2 9 9

a_no_duplicate = unique(A.', 'rows').'

a_no_duplicate = 2×3

1 2 7 9 2 3

a_no_duplicate_no_sort = unique(A.', 'rows','stable').'

a_no_duplicate = 2×3

7 2 1 3 2 9