How to generate a sparse matrix for a given array?

5 次查看（过去 30 天）

显示更早的评论

Benson Gou 2021-5-24

0
链接

此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/837788-how-to-generate-a-sparse-matrix-for-a-given-array

评论： Benson Gou 2021-5-25

采纳的回答： Matt J

在 MATLAB Online 中打开

Dear All,

I want to generate a sparse matrix B for a given array A. A contains two columns of indecis. For example,

A = [1 3;
4;
3;
5;
5;
5]

The sparse matrix B should be as follows:

B = [ 2  0 -1 -1  0;
      0  2 -1  0 -1;
     -1 -1  2  0  0;
     -1  0  0  2 -1;
      0 -1 -1 -1  3]

The characteristics of B:

Sum of each row is zero.
If we consider matrix A gives the information of edges of a graph, B(i,i) = sum of number of edges, B(i,j) = -1 if there is an edge between i and j.

Thanks a lot.

Benson

0 个评论
显示 -2更早的评论隐藏 -2更早的评论

请先登录，再进行评论。

请先登录，再回答此问题。

采纳的回答

Matt J 2021-5-25

0
链接

此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/837788-how-to-generate-a-sparse-matrix-for-a-given-array#answer_708260

编辑：Matt J 2021-5-25

在 MATLAB Online 中打开

B=laplacian( graph(A(:,1),A(:,2)) );

5 个评论
显示 3更早的评论隐藏 3更早的评论

Benson Gou 2021-5-25

yes, it works well. Thanks a lot.

Benson

Matt J 2021-5-25

You're welcome, but please Accept-click the answer that you deem best resolves your question.

请先登录，再进行评论。

更多回答（1 个）

the cyclist 2021-5-24

1
链接

此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/837788-how-to-generate-a-sparse-matrix-for-a-given-array#answer_706703

在 MATLAB Online 中打开

Here is one way:

A = [1 3;
     1 4;
     2 3;
     2 5;
     3 5;
     4 5];
d = max(A(:));
B = sparse(A(:,1),A(:,2),-1,d,d) + sparse(A(:,2),A(:,1),-1,d,d);
for ii = 1:d
    B(ii,ii) = -sum(B(ii,:));
end
disp(B)
   (1,1)        2
   (3,1)       -1
   (4,1)       -1
   (2,2)        2
   (3,2)       -1
   (5,2)       -1
   (1,3)       -1
   (2,3)       -1
   (3,3)        3
   (5,3)       -1
   (1,4)       -1
   (4,4)        2
   (5,4)       -1
   (2,5)       -1
   (3,5)       -1
   (4,5)       -1
   (5,5)        3