finding an item in an array

Hello,

I have an array of five items for example 1 2 2 2 4

How can I find the positions of the repeated items, i.e 2 2 2?

Thanks

Answer 1

[Aldin]

Here is my solution:

a = [ 1 2 2 2 4 ];

find(a==2)

   ans =

       2     3     4

[Daniel Shub]

+1 for simplicity. While this requires knowing what number is repeated and will fail if multiple numbers are repeated, it does answer the question.

[Aldin]

HERE IS THE COMBINATION OF Daniels AND my CODE:

x = [1 2 2 2 4 5 5 3 3 2];

a = unique(x);

[~,b] = unique(x, 'first');

[~,c] = unique(x, 'last');

ismember(x, a(b~=c))

the result will be: 0 1 1 1 0 1 1 1 1 1

(my code) if you want to get index:

find(ans==1)

result:

ans =

2 3 4 6 7 8 9 10

Answer 2

[Jonathan Sullivan]

http://www.mathworks.com/matlabcentral/fileexchange/28113-findseq

Answer 3

[MURTADHA ALDEER]

when I use findseq, I get this message

??? Undefined function or method 'findseq' for input arguments of type 'double'.

!

[Jonathan Sullivan]

Make sure you download the function. It is not built into MATLAB.

Answer 4

[MURTADHA ALDEER]

Oh, thank you

But could you help me and let me know how to download a function?

[Jonathan Sullivan]

There's a button in the top right that says "Download All." Click that one.

[MURTADHA ALDEER]

Sorry, Jonathan

I can not find this button

You mean it is in Matlab, or in Matlab website?

Thank you for your valuable efforts

[Oleg Komarov]

Diret link to download: http://www.mathworks.com/matlabcentral/fileexchange/28113-findseq?controller=file_infos&download=true

FEX page for findseq: http://www.mathworks.com/matlabcentral/fileexchange/28113-findseq

Answer 5

[Daniel Shub]

One of my uglier solutions ...

x = [1 2 2 2 4];
a = unique(x);
[~,b] = unique(x, 'first');
[~,c] = unique(x, 'last');
ismember(x, a(b~=c))

Answer 6

[Aldin]

HERE IS THE COMBINATION OF Daniels AND my CODE:

x = [1 2 2 2 4 5 5 3 3 2]; 
  a = unique(x); 
  [~,b] = unique(x, 'first'); 
  [~,c] = unique(x, 'last'); 
  ismember(x, a(b~=c)) 
  the result will be: 0 1 1 1 0 1 1 1 1 1
  (my code) if you want to get index:
  find(ans==1)

result: ans = 2 3 4 6 7 8 9 10

Answer 7

[MURTADHA ALDEER]

Thank you all for your answer, I was looking for the most repeated item

I sat with a friend and we found the solution, see below:

previous=[1 2 2 3 4]

    for lo = 1: length (previous)
        for lon = 1 : length (previous)

        H(lo,lon) = any(previous(lo)==previous(lon));

        end
    end

add = find(sum(H')==max(sum(H')))

add will return the positions of the repeated item (2).

Regards

[Daniel Shub]

If your question is now answered, then accept your answer and upvote anyone that helped.