How can I find matching rows from three out of four colomns

Question

Joanie 2014-5-15

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https://ww2.mathworks.cn/matlabcentral/answers/129712-how-can-i-find-matching-rows-from-three-out-of-four-colomns

评论： Henric Rydén 2014-5-19

I have a matrix with 4 columns, x y z and D, and a lot of rows. I want the program to find the rows where x, y and z are the same (so the first three colomns match) and add the corresponding D value of these matching rows. When the matching rows are found only one stays in the matrix with the new D value. To make it a little more complicated I like to attach a tolerance for what the matching values can diverge.

For example:

x y z D

1 2 3 4

2 4 6 8

1 2 3 5

New one:

x y z D

1 2 3 9

2 4 6 8

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Answer 1

Henric Rydén 2014-5-15

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https://ww2.mathworks.cn/matlabcentral/answers/129712-how-can-i-find-matching-rows-from-three-out-of-four-colomns#answer_136888

编辑：Henric Rydén 2014-5-15

在 MATLAB Online 中打开

This solution might not be as simple and elegant as the one Andrei Bobrov provided, but it allows for a tolerance level.

% Example data
A=[ 1    2  3 ; ...
    2    4  6 ; ...
    1.05 2  3 ; ...
    1    52 3 ; ...
    2    4  6 ; ...
    1.05 2  3 ; ...
    5    2  3 ; ...
    1    52 3 ; ...
    5    2  3 ; ...
    ];
D = [4; 8; 5; 1; 2; 3; 5; 7; 8];
% Vector to track which have been processed and how they are grouped
processed = zeros(size(A,1),1);
% Tolerance level
tol = .1;
row = 1;
while ~all(processed)
    % Only check rows that havent been matched yet
    if ~processed(row)
        % Take out the row you want to compare to the others
        curRow = A(row,:);
        % Subtract that row from all rows in A
        subtractedA  = A - repmat(curRow,size(A-1,1), 1);
        % Check to see if they are within the tolerance level
        matchingRows = all((subtractedA <= tol & subtractedA >= -tol),2);
        % Mark the rows as processed
        processed(matchingRows) = row;
        % Update A to the mean of all matches
        A(matchingRows,:) = repmat(mean(A(matchingRows,:),1),sum(matchingRows),1);
        % Sum the D values that matches
        D(matchingRows) = sum(D(matchingRows));
    end
    % Check the next row
    row = row + 1;
end
% Results
[A(unique(processed),:) D(unique(processed))]

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Joanie 2014-5-16

It works thank you!!

Henric Rydén 2014-5-19

You're welcome

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Answer 2

Andrei Bobrov 2014-5-15

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此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/129712-how-can-i-find-matching-rows-from-three-out-of-four-colomns#answer_136876

编辑：Andrei Bobrov 2014-5-17

在 MATLAB Online 中打开

d = [1 2 3 4
2 4 6 8
1 2 3 5];
[a,b,c] = unique(d(:,1:end-1),'rows');
out = [a, accumarray(c,d(:,end))];

add

d0 =[[  1.1            2          3.2
2            4            6
1.2            2          3.3
2.09           3.96        6.05
1.05          1.99        3.25],randi(25,5,1)];
eps1 = .1;
d = d0(:,1:end-1);
l = bsxfun(@(x,y)abs(x-y)<=eps1,permute(d,[1 3 2]),permute(d,[3 1 2]));
[ii,jj] = find(triu(all(l,3),1));
a = num2cell(unique([[ii;ii],[ii;jj]],'rows'),1);
out = [cell2mat(accumarray(a{:},[],@(x){mean(d0(x,1:end-1))})),...
                                     accumarray(a{1},d0(a{2},end))];