Check common elements in two vectors and remove them from both the vectors leaving any duplicate. (Example Inside)

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Edoardo Busetti 2019-4-24

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编辑： Andrei Bobrov 2019-4-24

Suppose I have two vectors:

A = [1 2 3 4 4 4 5 5 6]

B = [2 4 5 5 9 ]

I want to get:

new_A = [1 3 4 4 6]

new_B = [9]

For example let's say that the vector A contains the elements of a numerator (1*2*3*4*4*4*5*5*6) and the vector B the elements of a denominator (2*4*5*5*9) and I want to simplify numerator and denominator.

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David Wilson 2019-4-24

Try the intersect function and friends (such as setxor).

Edoardo Busetti 2019-4-24

Thank you, intersect did it

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Answer 1

KSSV 2019-4-24

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在 MATLAB Online 中打开

A = [1 2 3 4 4 4 5 5 6]
B = [2 4 5 5 9 ]
new_A = setdiff(A,B) 
new_B = setdiff(B,A) 

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Edoardo Busetti 2019-4-24

This doesn't do it, it deletes values that appear one time in a vector but multiple times in the other

David Wilson 2019-4-24

Is this correct though? You've dropped all the 4's, I think the original poster only wanted one dropped in new_A.

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Answer 2

Guillaume 2019-4-24

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编辑：Guillaume 2019-4-24

在 MATLAB Online 中打开

"Thank you, intersect did it"

intersect on its own will not do it since all set membership functions (setdiff, setxor, union, ismember, etc.) completely ignores duplicate elements.

You would have to compute the histogram of each to solve your problem and work out the intersection of that.

A = [1 2 3 4 4 4 5 5 6]
B = [2 4 5 5 9]
%get unique values of each set
uA = unique(A);
uB = unique(B);
%compute histogram of each set
countA = histcounts(A, [uA, Inf]);
countB = histcounts(B, [uB, Inf]);
%find common values of each set
[~, locA, locB] = intersect(uA, uB);
%minimum count of duplicate from each set
removecount = min(countA(locA), countB(locB));
%remove that minimum count from the total count in each set
countA(locA) = countA(locA) - removecount;
countB(locB) = countB(locB) - removecount;
%and recreate sets based on the new count
newA = repelem(uA, countA)
newB = repelem(uB, countB)

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Answer 3

Andrei Bobrov 2019-4-24

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编辑：Andrei Bobrov 2019-4-24

a1 = unique([A(:);B(:)]);
s = size(a1);
[~,iA] = ismember(A(:),a1);
[~,iB] = ismember(B(:),a1);
ii = (accumarray(iA,1,s) - accumarray(iB,1,s)).*[1,-1];
ii = ii.*(ii > 0);
new_A = repelem(a1,ii(:,1));
new_B = repelem(a1,ii(:,2));