In a sorted vector ,how do I compare first element to other elements and then find if there are any duplicates , if yes take their indexes and replace it with 0
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A = [ 1, 1 , 2, 3, 4]
I want to first compare first element to all other elements, if there is any duplicate (like 1, 1 in this example) I need to replace it with 0.
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Stephen23
le 6 Nov 2018
Modifié(e) : Stephen23
le 6 Nov 2018
For a sorted row vector. Find duplicates of the first element, as you requested:
>> A = [1,1,2,3,4];
>> X = A(1)==A;
>> X(1) = false;
>> A(X) = 0
A =
1 0 2 3 4
Or perhaps you meant to find all duplicates, not just of the first element:
>> A = [1,1,2,3,4];
>> X = [false,diff(A)==0];
>> A(X) = 0
A =
1 0 2 3 4
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Stephen23
le 15 Nov 2018
Modifié(e) : Stephen23
le 15 Nov 2018
PS: taking a wild guess here, that you want to perform this for each page (i.e. along the third dimension) independently:
>> C = {[9,3,7;6,3,8;3,7,9],[8,4,8;2,6,7;2,9,5]};
>> A = cat(3,C{:})
A(:,:,1) =
9 3 7
6 3 8
3 7 9
A(:,:,2) =
8 4 8
2 6 7
2 9 5
>> DM = sort(sort(A,1),2)
DM(:,:,1) =
3 3 7
3 6 8
7 9 9
DM(:,:,2) =
2 4 5
2 6 7
8 8 9
>> X = DM(1,1,:)==DM;
>> [~,~,P] = ind2sub(size(X),find(X));
>> V = accumarray(P,1,[],@(v)1/sum(v));
>> A(X) = V(P);
>> A(~X) = 0
A(:,:,1) =
0.33333 0.33333 0.00000
0.33333 0.00000 0.00000
0.00000 0.00000 0.00000
A(:,:,2) =
0.50000 0.00000 0.00000
0.50000 0.00000 0.00000
0.00000 0.00000 0.00000
If that is not the output that you expect then please show me what output you need to get.
Plus de réponses (3)
madhan ravi
le 6 Nov 2018
Modifié(e) : madhan ravi
le 6 Nov 2018
A = [ 1, 1, 2, 3, 4];
[~,c,~]=(unique(A,'first'));
idx=(ismember((1:numel(A)),c));
A(~idx)=0
c is the index of unique values in A the left out indices contain duplicate values. The above method works for arbitrary vectors too not only for sorted vector.
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Bruno Luong
le 15 Nov 2018
Modifié(e) : Bruno Luong
le 15 Nov 2018
For array with finite elements
A.*[1,diff(A)~=0]
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