Question

I am trying to sort the columns of a matrix based on the another vector values in a
fast way in matlab.
Let assume I have a reference vector:

a = [1 8 3];

And the matrix I wanna sort by rows

b =[2 3 4
    5 6 4
    1 2 1];

And I want the result based on the vector a if the sorted a is

 a = [8 3 1]

the sorted matrix will be now

b = [3 4 2 
     6 4 5
     2 1 1];

So the index of the first vector is the same with the index of the columns
So we sort columns based on the values of the vector.

Answer 1

In Matlab the sort function returns two variables, the first is the sorted vector/matrix and the second is a set of indices that can be combined with the original data to produce the sorted values.

A = [ 5 4 1 2 3 ];

[A_sorted1, idx] = sort(A);

A_sorted2 = A(idx);

A_sorted1 and A_sorted2 are equivalent.

If the number of rows in b is equal to the number of elements in a then you can simply use:

[~, idx] = sort(a);
b_sorted = b(idx,:);

And if you want to sort by columns use:

b_sorted = b(:,idx);