# Sorting a matrix according to another one

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Mattia Salomone on 31 May 2023
Commented: Mattia Salomone on 1 Jun 2023
Dear all,
I have the following problem to solve.
clear
clc
% A matrix defined as follows
A=[11 0.001 3
11 0.001 4
12 0.003 5
9 0.002 6
8 0.000 7
10 0.004 8
8 0.000 9
9 0.002 10];
% B matrix is the reference one
B=[8 0.000
8 0.000
9 0.002
10 0.004
9 0.002
11 0.001
11 0.001
12 0.003];
I want to sort A such that the first two columns coincide with B (and sort the other A column in agreement with this, of course). I used this code, but the problem is that since in B I have repeted conditions the result is not the one I desire.
[~,Y]=ismember(A(:,1:2),B,'rows');
[~,Z]=sort(Y);
C=A(Z,:);
% C=8 0.000 7
% 8 0.000 9
% 9 0.002 6
% 9 0.002 10
% 10 0.004 8
% 11 0.001 3
% 11 0.001 4
% 12 0.003 5
But what I want is
% C=8 0.000 7
% 8 0.000 9
% 9 0.002 6
% 10 0.004 8
% 9 0.002 10
% 11 0.001 3
% 11 0.001 4
% 12 0.003 5
Do you have any suggestions that don't involve using nested loops and if conditions?
Thank you very much for your attention!
Mattia
##### 2 CommentsShow 1 older commentHide 1 older comment
Mattia Salomone on 31 May 2023
Thanks for your answer. Well in this case the order in which they appear in C should be the one they have in A. In this case with [8 0], for example, I want
[8 0 7
8 0 9]
Because in A they appear with this order.

Torsten on 31 May 2023
Edited: Torsten on 31 May 2023
A = [11 0.001 3
11 0.001 4
12 0.003 5
9 0.002 6
8 0.000 7
10 0.004 8
8 0.000 9
9 0.002 10];
% B matrix is the reference one
B = [8 0.000
8 0.000
9 0.002
10 0.004
9 0.002
11 0.001
11 0.001
12 0.003];
[~,idx] = sortrows(A,[1 2]);
[~,jdx] = sortrows(B,[1 2]);
C = A(idx(jdx),:)
C = 8×3
8.0000 0 7.0000 8.0000 0 9.0000 9.0000 0.0020 6.0000 10.0000 0.0040 8.0000 9.0000 0.0020 10.0000 11.0000 0.0010 3.0000 11.0000 0.0010 4.0000 12.0000 0.0030 5.0000
Mattia Salomone on 1 Jun 2023
Thank you very much for your help!