How to filter duplicate entries

Question

Mekala balaji 2018-8-8

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此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/414060-how-to-filter-duplicate-entries

评论： Mekala balaji 2018-8-9

采纳的回答： Adam Danz

在 MATLAB Online 中打开

Hi,

I have below entries (cell array matrix),

FirstEntry  SecondEntry Index Score
A               B        5     25
C               D        62    8  
C               K        31    2
B               A        6     25
K               C        9     2

The entry A & B (in row 1)is same as B & A(in row 4) (without consider its first entry or second entry), I only want to keep one entry for this kind of entries. Likewise, row 3 (c & K) is same as row 5 (K & C)

My desired output:
FirstEntry  SecondEntry Index Score
A               B        5     25
C               D        62    8  
C               K        31    2

Kindly some one help, many thanks in advance,

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Answer 1

Adam Danz 2018-8-8

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链接

此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/414060-how-to-filter-duplicate-entries#answer_332029

编辑：Adam Danz 2018-8-8

在 MATLAB Online 中打开

Your original cell array is named 't'.

t = {
'A'              'B'        5     25
'C'               'D'        62    8  
'C'               'K'        31    2
'B'               'A'        6     25
'K'               'C'        9     2};

'unqIdx' is an index of row numbers of 't' that are unique.

'desired' is your unique array without duplicates.

[~, unqIdx] = unique(cellfun(@strcat, sort(t(:,[1,2])')'), 'rows'); 
desired = t(unqIdx, :);

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Adam Danz 2018-8-8

在 MATLAB Online 中打开

Sure. The best way is to step through the functions starting from the inside out.

1) We want to sort the rows of the first 2 columns of 't' so that {'B' 'A'} becomes {'A', 'B'}. The tick marks (') merely transpose the array which really could be avoided but I included it so the orientation of the data is consistent.

    sort(t(:,[1,2])')'
    ans =
      5×2 cell array
        {'A'}    {'B'}
        {'C'}    {'D'}
        {'C'}    {'K'}
        {'A'}    {'B'}
        {'C'}    {'K'}

2) Now we want to join (concatenate) the two columns of strings into single strings. {'A' 'B'} becomes 'AB'.

cellfun(@strcat, sort(t(:,[1,2])')')
ans =
  5×2 char array
    'AB'
    'CD'
    'CK'
    'AB'
    'CK'

3) Now we want to know which rows of the above character array are unique. The 2nd output of unique() gives us those row numbers.

[~, unqIdx] = unique(cellfun(@strcat, sort(t(:,[1,2])')'), 'rows')
unqIdx =
   1
   2
   3

4) Finally we use those row numbers (indices) to create the unique version of 't'.

t(unqIdx, :)
ans =
  3×4 cell array
    {'A'}    {'B'}    {[ 5]}    {[25]}
    {'C'}    {'D'}    {[62]}    {[ 8]}
    {'C'}    {'K'}    {[31]}    {[ 2]}

Adam Danz 2018-8-9

在 MATLAB Online 中打开

I see. Here's the updated code that works with the old and new dataset. I could no longer do it in 1 line of code. The new version uses 2 lines and the use of cellfun() is no longer necessary. I also added the 'stable' parameter to unique() so that your final unique array is in the same order as your input array.

tSort = sort(t(:,[1,2])')';
[~, unqIdx] = unique(strcat(tSort(:,1), tSort(:,2)), 'rows', 'stable')
t(unqIdx, :)

Mekala balaji 2018-8-9

Thanks Sir,

It works.

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How to filter duplicate entries

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