How to find shared elements in a matrix

2017 3 12
1 个回答
回答已采纳
更新时间：2017 3 13
6 次查看（30 天）

0 个投票

Hi,
I have a zeros and ones vector called P. And a zeros and ones matrix called A, the matrix has a size nXn. The ones index in vector P, represents the raw in matrix A. For example if P=[0 1 0 1 0 0], then the corresponding rows in A are rows 2,4.
  1. (shared directly) I would like to find if A(2,4) or A(4,2) are both ones. The output is 4,2
  2. (shared indirectly) Now I want to find which elements i A(2,:) and A(4,:) are shared e.g have the same value. for example A(2,3) and A(4,3) both have ones, then I would get 3. The output is [2,3],[4,3]
I only care about the ones in both the vector P and matrix A. I have no interest in zero elements.

2 个评论
显示 无 隐藏 无

Geoff Hayes
Geoff Hayes 2017-3-12
Saleh - will your P array only ever have two ones (so you will only be ever comparing two rows)? Or can P have more than two ones in which case you would be comparing every possible row pair?
Saleh Almasabi
Saleh Almasabi 2017-3-12
Hi Geoff,
The P array might have two or more ones. I might need to compare two or more. I thought of adding the corresponding rows in A, two at a time. Then I would use the (find) command. (long but will work)
But the shared indirectly, especially if its (three layers) or more, is going to be tricky.

请先登录，再进行评论。

请先登录，再回答此问题。

 采纳的回答

Roger Stafford
Roger Stafford 2017-3-13

0 个投票

D = nchoosek(find(P==1),2);
D = D(A(D(:,1)+n*(D(:,2)-1))==1 & A(D(:,2)+n*(D(:,1)-1))==1,:);
The two elements in each row of D are the possible indices such as 2,4 you mentioned in the “shared directly” part.

更多回答（0 个）

类别

在 帮助中心 和 File Exchange 中查找有关 Matrix Indexing 的更多信息

标签

Community Treasure Hunt

Find the treasures in MATLAB Central and discover how the community can help you!

Start Hunting!

Translated by