indexing groups of elements in a vector in a certain way

Question

LH 2024-7-23，17:25

0
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此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/2139641-indexing-groups-of-elements-in-a-vector-in-a-certain-way

评论： Voss 2024-7-23，18:35

采纳的回答： Voss

在 MATLAB Online 中打开

Hi all,

I have two vectors A and B where they look like the following:

%vector A
A = [1 1 
1
1
1
2
2
2
3 
3
3 
3];
%vector B
B = [12 2
3
3
2
1
1
3
2
1
1
1];

The second column of each of these vectors corresponds to the index of each row. As can be seen, vector A has 3 main "groups". For each of these groups, there are 2 groups that corrspond to them in vector B. For example, for group 1 in vector A there are two groups 2 and 3 in vector B, and so on do forth.

It can be seen that in total vector B has 6 main groups. And here where I need help!

I want to reindex the rows of vector B without changing its elements order so that it contains 6 gorups and looks like:

%vector C
C = [12 1
2
2
1
3
3
4
5
6
6
6];

In this way, group 1 in vector A, has groups 1 and 2 in the new vector C. Group 2 in vectorA has groups 3 and 4 in vectro C. Group 3 in vector A has groups 5 and 6 in vector C.

Any help would be appreicted.

Thanks.

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Answer 1

Voss 2024-7-23，18:02

0
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此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/2139641-indexing-groups-of-elements-in-a-vector-in-a-certain-way#answer_1489556

在 MATLAB Online 中打开

%matrix A
A = [1 1 
1
1
1
2
2
2
3 
3
3 
3];
%matrix B
B = [12 2
3
3
2
1
1
3
2
1
1
1];
[~,~,idx] = unique([A(:,2),B(:,2)],'rows','stable');
%matrix C
C = [B(:,1) idx];
disp(C)
   1
   2
   2
   1
   3
   3
   4
   5
   6
   6
   6