How do I get the maximum of repetitive elements in certain portions of a matrix?

3 次查看（过去 30 天）

Antonio 2018-1-18

0
链接

此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/377700-how-do-i-get-the-maximum-of-repetitive-elements-in-certain-portions-of-a-matrix

评论： Star Strider 2018-1-18

I have a 2000x2 matrix, and "for each 10x2 segment of this matrix", I need to calculate the maximum of corresponding values (second column) of repetitive values (first column) in the matrix. Like if the 3rd 10x2 segment of the matrix is this:

 ...
[2 20;
30;
40;
100;
110;
120;
130;
140;
240;
260]
 ...

I want to get this:

 ...
[2 40;
7 140;
15 260]
 ...

And so on. I have written the following but it gives me the maximum of repetitive elements through the "whole matrix":

[uv,~,idx] = unique(A(:,1));
B = [uv accumarray(idx,A(:,2),[],@max)];

But again, I need to do this "for each separate 10x2 segments of the matrix", and then store the results in a 'whatever x 2' sized matrix! Does anyone have any ideas how I could do this?

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

Star Strider 2018-1-18

1
链接

此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/377700-how-do-i-get-the-maximum-of-repetitive-elements-in-certain-portions-of-a-matrix#answer_300613

在 MATLAB Online 中打开

The only way I can see to do this is with a loop that selects and analyses each 10-row segment.

This works:

A = [2 20;
30;
40;
100;
110;
120;
130;
140;
240;
260
20;
30;
40;
100;
110;
120;
130;
140;
240;
260    
20;
30;
40;
100;
110;
120;
130;
140;
240;
260];
for k1 = 1:10:size(A,1)
    T = A(k1:k1+9,:);
    [uv,~,idx] = unique(T(:,1));
    B{ceil(k1/10)} = [uv accumarray(idx,T(:,2),[],@max)];   % Output Cell Array               
end