CODEWITHSUNDEEP
matlab
popist
popist

Reputation: 83

Find duplicates in a matrix

consider a matrix:

a = [1 2 
     1 3
     2 3
     4 5
     6 1]

I want to find duplicates for every unique element of a and take the rows of them to different matrices. For example here lets say that the answer for number 1 is:

a1 = [1 2
      1 3
      6 1]

The answer for number 2 is:

a2 = [1 2
      2 3]

The answer for number 3 is:

a3 = [1 3
      2 3]

and so on for every unique elements of matrix a. Any suggestions?

Upvotes: 0

Views: 325

Answers (2)

Sardar Usama
Sardar Usama

Reputation: 19689

This will do it:

temp=unique(a);
for k=1:numel(temp)
    [r,~]=find(a==temp(k));
    assignin('base', ['a' num2str(k)], a(sort(r),:)) 
end

Results:-

>> a1

a1 =

     1     2
     1     3
     6     1

>> a2

a2 =

     1     2
     2     3

>> a3

a3 =

     1     3
     2     3

>> a4

a4 =

     4     5

>> a5

a5 =

     4     5

>> a6

a6 =

     6     1

Upvotes: 1

Suever
Suever

Reputation: 65470

You can use any to check if any element of a row contains the value you want. This will return a logical array that is true where the row contained the value. You can then use this to grab the relevant rows of a.

result = a(any(a == value, 2), :);

We could create an anonymous function that does this for you.

rows_that_contain_value = @(A, value)A(any(A == value, 2), :);

Then we can use this like this

a = [1 2 
     1 3
     2 3
     4 5
     6 1]

a1 = rows_that_contain_value(a, 1);
a2 = rows_that_contain_value(a, 2);
a3 = rows_that_contain_value(a, 3);

If we want to do this for all unique values in a, we can do something like the following.

groups = arrayfun(@(x)rows_that_contain_value(a, x), unique(a), 'uniformoutput', 0);

Upvotes: 0

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