count number of elements for each slice of a vector

Question

LH 2024-7-10，15:28

0
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https://ww2.mathworks.cn/matlabcentral/answers/2136258-count-number-of-elements-for-each-slice-of-a-vector

评论： LH 2024-7-10，15:57

采纳的回答： Aquatris

在 MATLAB Online 中打开

Hi all,

I have the folloiwng vector:

A = [2 1;
1;
2;
2;
2;
1;
1 ;
1;
2;
2];

You can see that the second column is either 1 or 2. I would liek to count the slices that has the same number without repetition, meaning that I want to count the first two number that have number 1 in their second column seprately from the three down the vectro (each slice separatly). As a result I wouldl ike to have something like:

num = [2 3 3 2];

Any help would be appreicted.

Thanks.

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Answer 1

Aquatris 2024-7-10，15:40

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在 MATLAB Online 中打开

Here is one simple way:

A = [2 1;
    3 1;
    4 2;
    5 2;
    6 2;
    7 1;
    8 1;
    7 1;
    5 2;
    6 2];
 
tmp =  find(diff(A(:,2))~=0); % find indeces where 2nd column values change
num = [tmp(1) diff(tmp') size(A,1)-tmp(end)] % desired output
num = 1x4
     2     3     3     2
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