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Finding Duplicate Values per Column

Asked by RDG

RDG (view profile)

on 22 Oct 2011
Latest activity Edited by Clemens

Clemens (view profile)

on 19 Mar 2014

Greetings, suppose Column A has these values - 7 18 27 42 65 49 54 65 78 82 87 98

Is there a way to compare the values (row by row) and search for duplicates? (I'm using Matlab R2010b)I don't want the duplicated values to be removed.

Thanks.

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RDG

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3 Answers

Answer by Jan Simon

Jan Simon (view profile)

on 22 Oct 2011
Accepted answer
A = [7 18 27 42 65 49 54 65 78 82 87 98];
[n, bin] = histc(A, unique(A));
multiple = find(n > 1);
index    = find(ismember(bin, multiple));

Now the values A(index) appear mutliple times.

1 Comment

Teik Yee

Teik Yee (view profile)

on 19 Nov 2012

thx

Jan Simon

Jan Simon (view profile)

Answer by the cyclist

the cyclist (view profile)

on 22 Oct 2011

Here's a slightly different way:

X = [1 2 3 4 5 5 5 1];
uniqueX = unique(X);
countOfX = hist(X,uniqueX);
indexToRepeatedValue = (countOfX~=1);
repeatedValues = uniqueX(indexToRepeatedValue)
numberOfAppearancesOfRepeatedValues = countOfX(indexToRepeatedValue)

3 Comments

Harold

Harold (view profile)

on 13 Apr 2012

Is there a way that I can use this approach for a cell array. Suppose I have a 1x4 cell array and each cell contains a (x,y) co-ordinates. Can I somehow modify your solution to search for duplicate cells and get rid of them?

Yowh

Yowh (view profile)

on 19 Nov 2012

Harold can you give an example of your cell array variable ?

Jan Simon

Jan Simon (view profile)

on 19 Nov 2012

@Yowh: It is unlikely, that Harold listens to comments after 8 months.

the cyclist

the cyclist (view profile)

Answer by Hannes Greim

Hannes Greim (view profile)

on 19 Jan 2013

you can use "tabulate" for cell arrays.

1 Comment

Clemens

Clemens (view profile)

on 19 Mar 2014

Working only for versions after 2012 with the intro of tables.

Hannes Greim

Hannes Greim (view profile)

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