Question

I have data like the following matrix:
A = [2 5 10 4 10; 2 4 5 1 2; 6 2 1 5 4];

A =

 2     5    10     4    10
 2     4     5     1     2
 6     2     1     5     4

I would like to sort the by the last row based on the following criteria:

if the difference between the first element (in the third row) and second element (in the third row) is less than or equal to 2 — then move that column (the second in this case two columns to the right). Then do this for all columns until no two elements (of the last row) are within a difference of 2)

B =

 2     5     4    10    10
 2     4     1     5     2
 6     2     5     1     4

Where (6-2 = 4) (2-5 = 3) (5-1 = 4) (1-4 = 3)

Ultimately difference between all elements of the last row and element next to it is greater than 2.

Any suggestions?

Answer 1

This is one possible solution:

A = [2 5 10 4 10; 2 4 5 1 2; 6 2 1 5 4];

B = A;

MatrixWidth = size(A, 2);

CurIndex = 1;

%# The second-last pair of the bottom row is the last pair to be compared.
while(CurIndex+2 <= MatrixWidth)
    Difference = abs(A(3,CurIndex) - A(3,CurIndex+1));

    %# If the right side of comparison is not yet the second-last index.
    if ((Difference <= 2) && (CurIndex+3 <= MatrixWidth))
        B = [ B(:, 1:CurIndex), B(:, CurIndex+2), B(:, CurIndex+1), B(:, CurIndex+3:end) ];
    %# If the right side of the comparison is already the second-last index.
    elseif (Difference <= 2)
        B = [ B(:, 1:CurIndex), B(:, CurIndex+2), B(:, CurIndex+1) ];
    end

    CurIndex = CurIndex + 1;
end