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finding an item in an array

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MURTADHA ALDEER
MURTADHA ALDEER on 20 Mar 2012
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

Answers (7)

Aldin
Aldin on 20 Mar 2012
Here is my solution:
a = [ 1 2 2 2 4 ];
find(a==2)
ans =
2 3 4
  2 Comments
Aldin
Aldin on 20 Mar 2012
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

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MURTADHA ALDEER
MURTADHA ALDEER on 20 Mar 2012
when I use findseq, I get this message
??? Undefined function or method 'findseq' for input arguments of type 'double'.
!
  1 Comment
Jonathan Sullivan
Jonathan Sullivan on 20 Mar 2012
Make sure you download the function. It is not built into MATLAB.

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MURTADHA ALDEER
MURTADHA ALDEER on 20 Mar 2012
Oh, thank you
But could you help me and let me know how to download a function?
  3 Comments
Oleg Komarov
Oleg Komarov on 25 Mar 2012
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

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Daniel Shub
Daniel Shub on 20 Mar 2012
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))

Aldin
Aldin on 21 Mar 2012
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

MURTADHA ALDEER
MURTADHA ALDEER on 22 Mar 2012
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
  1 Comment
Daniel Shub
Daniel Shub on 25 Mar 2012
If your question is now answered, then accept your answer and upvote anyone that helped.

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