How to reduce this matrix?

Question

Anderson 2016-4-21

0
链接

此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/280316-how-to-reduce-this-matrix

回答： Azzi Abdelmalek 2016-4-21

Suppose that M=[1 0.1 1.1; 1 0.1 1.1; 3 0.1 1.2; 2 0.2 3; 1 2 4; 2 2 4; 2 3 5];

based on the second column, for repeated values of the second column, sum the elements of column 1 when the elements of column 3 are equals. If the elements of column 3 are different, do a weighted average using column 1.

For the matrix M above, the output should be:

M_out = [5 0.1 1.16; 2 0.2 3; 3 2 4; 2 3 5];

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。

Answer 1

Azzi Abdelmalek 2016-4-21

0
链接

此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/280316-how-to-reduce-this-matrix#answer_218918

在 MATLAB Online 中打开

M=[1 0.1 1.1; 1 0.1 1.1; 3 0.1 1.2; 2 0.2 3; 1 2 4; 2 2 4; 2 3 5]
[ii,jj,kk]=unique(M(:,2))
a=accumarray(kk,M(:,1))
b=accumarray(kk,1:numel(kk),[],@(x) sum(M(x,1).*M(x,3))/sum(M(x,1)));
M_out =[a ii b]