How do I remove a set of repeated values in a x by 2 matrix?

Question

MR 2020-3-22

0
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https://ww2.mathworks.cn/matlabcentral/answers/512174-how-do-i-remove-a-set-of-repeated-values-in-a-x-by-2-matrix

关闭： MATLAB Answer Bot 2021-8-20

For example,

Given the matrix:

matrix =

18 4

12 11

11 12

4 18

I want to get rid of the repeated values that happen after the first two rows to just get

matrix =

18 4

12 11

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MR 2020-3-22

if it matches with another in a different row then we are getting rid of it... the only time we wanna keep the number in the next column is if they're in the same row..

for example for this matrix

matrix =

23 2

22 4

21 6

19 8

14 14

8 19

6 21

4 22

2 23

I want to just reduce it down to

23 2

22 4

21 6

19 8

14 14

Hope that makes sense

Rik 2020-3-25

In response to your flag ("I posted an unclear question and did not receive help"):

You did receive help. Why don't you try describing the question more clearly if you think that is the problem?

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Answer 1

Ajay Kumar 2020-3-22

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https://ww2.mathworks.cn/matlabcentral/answers/512174-how-do-i-remove-a-set-of-repeated-values-in-a-x-by-2-matrix#answer_421284

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unique(matrix)

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Answer 2

Rik 2020-3-25

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https://ww2.mathworks.cn/matlabcentral/answers/512174-how-do-i-remove-a-set-of-repeated-values-in-a-x-by-2-matrix#answer_421884

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I think the code below is what you need. There may be much more efficient methods, but this will do as long as this will not be the bottleneck in your workflow.

clc
v=[18    4
    12   11
    11   12
    4     18];
remove_duplicate_rows(v)
v=[23     2
    22     4
    21     6
    19     8
    14    14
    8    19
    6    21
    4    22
    2    23];
remove_duplicate_rows(v)
function v=remove_duplicate_rows(v)
keeprows=false(size(v,1),1);
keeprows(1)=true;
for r=2:numel(keeprows)
    %check if the values are already in the rows that we want to keep
    %compare against numel(unique(v(r,:))) to catch repeated values
    if numel(setdiff(v(r,:),v(keeprows,:)))==numel(unique(v(r,:)))
        keeprows(r)=true;
    end
end
v=v(keeprows,:);
end