How to link two arrays?

Dear all,

I have two arrays:

A = [1,2,3,4,5,6,7,8,9,10];
B = [11,12,13,14,15,16,17,18,19,20];

If A became New_A = [4,3,2,1,10,9,8,7,6,5];

Then how to apply the same change to B such that

New_B = [14,13,12,11,20,19,18,17,16,15].

Any help will be appreciated.

Meshoo

Answer 1

[Stephen23]

Assuming that the elements are unique, then ismember will work:

>> A = [1,2,3,4,5,6,7,8,9,10];
>> B = [11,12,13,14,15,16,17,18,19,20];
>> New_A = [4,3,2,1,10,9,8,7,6,5];
>> [~,idx] = ismember(New_A,A);
>> New_B = B(idx)
New_B =
   14   13   12   11   20   19   18   17   16   15

[Meshooo]

Thank you very much.

Answer 2

[Jan]

If A contains the sorted numbers from 1 to n as in your example, the solution is easy:

B_new = B(A_new);

But maybe this matters the example data for the forum only.

[Meshooo]

Thank you Jan. Yeah I have more complex situations and it is not always serial numbers.