Reordering columns based on first row?

Commented on this post, but posting as a question here.

Suppose I have a matrix:

A = [
    5        4        1        2
    0.5      0.7      0.1     0.9
    0.9      0.4      0.3     0.2];

I'd like to use my first row as an index, so that my matrix is organized in an ascending order.

I know I can use sort:

[~,idx] = sort(A(1,:));
B = A(:,idx)

but this would give me a 3 by 4 matrix. I'd like a 3 by 5 matrix, such that the output looks like this:

1.0000    2.0000    0.0000   4.0000    5.0000
0.1000    0.9000    0.0000   0.7000    0.5000
0.3000    0.2000    0.0000   0.4000    0.9000

(doesn't have to be zeros as long as the column is empty)

I'd appreciate any help with this--thanks so much in advance!

Answer 1

[Voss]

Using the elements of the first row of A as column indices in B:

A = [
    5        4        1        2
    0.5      0.7      0.1     0.9
    0.9      0.4      0.3     0.2];

B = zeros(size(A,1),max(A(1,:)));

B(:,A(1,:)) = A

B = 3×5

1.0000 2.0000 0 4.0000 5.0000 0.1000 0.9000 0 0.7000 0.5000 0.3000 0.2000 0 0.4000 0.9000

[Jadyn]

I don't know why I can't accept/upvote your answer but this is exactly what I was looking for--thank you so much!!

[Voss]

You're welcome!