Matrix problem for same values of column

Question

Anu Sharma 2019-9-2

0
链接

此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/478555-matrix-problem-for-same-values-of-column

回答： Andrei Bobrov 2019-9-2

A=[29.78         5	 8
97         8	11
98         4	12
05	12	13
78         1	16
53	26	29
43	 2	32
94	11	33
57	15	35
43	17	36
49        23	37
69	37	38
97	28	39
25	25	40
36	36	41
24  	18	42
39	39	44
93	16	45
83	30	46
09	40	47
58	24	48
61	41	49
41	48	50]

and i want

output =[22.98    4   12
         25.53   26   29
         21.43    2   32
         29.94   11   33
         29.57   15   35
         28.43   17   36
         13.69   37   38
         26.97   28   39
          4.24   18   42
         29.93   16   45
         25.83   30   46
         26.09   40   47
         28.61   41   49
         29.41   48   50 ]

No value in column 2, 3 get repeated and in case of repeated value in any of the column(2,3) the higest value of column 1 is as the output.

For example, in row 1, 2 and 8. column (2,3) have values as

[ 5  8
  8 11
 11 33]

Among these 3 rows row 8, ie. [29.94 11 33] have the highest value so only this row will be the output. all other row like [29.78 5 8] and [24.97 8 11]will be elimanted.

simillarly,

for row 3 = [22.98 4 12]

And 4 = [21.05 12 13]

row 3= [22.98 4 12]

will be output and row 4 will get eliminated.

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Stephen23 2019-9-2

编辑：Stephen23 2019-9-2

Is the row

28.43 17 36

correct in your example output array? Following your explanation, these rows are one group:

28.43	17	36
...
27.36	36	41
...
28.61	41	49

of which the last row has the highest values in the first column (and the last row is in your output array). But why do you keep the first row as well?

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Answer 1

Stephen23 2019-9-2

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链接

此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/478555-matrix-problem-for-same-values-of-column#answer_390058

编辑：Stephen23 2019-9-2

N = size(A,1);
X = ones(N,1); % group numbers
Z = true(N,1); % logical index
V = 1; % group number
for k = 2:N % for each row...
    Y = A(k,2)==A(1:k-1,3); % check if any matching rows.
    if any(Y)
        X(k) = X(Y); % copy group number (assumed scalar).
        W = X(k)==X(1:k-1); % logical index of that group.
        if all(A(k,1)>A(W,1))
            Z(W) = false; % current val > prev vals.
        else
            Z(k) = false; %  prev val > current val.
        end
    else % no matching rows:
        V = V+1; % increment group number.
        X(k) = V;
    end
end
B = A(Z,:) % output matrix

Giving:

B =
        22.98            4           12
        25.53           26           29
        21.43            2           32
        29.94           11           33
        29.57           15           35
        13.69           37           38
        26.97           28           39
         4.24           18           42
        29.93           16           45
        25.83           30           46
        26.09           40           47
        28.61           41           49
        29.41           48           50

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Stephen23 2019-9-2

"In which variable ,output matrix is storing. "

B

Anu Sharma 2019-9-2

Thankyou so much..

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Answer 2

Andrei Bobrov 2019-9-2

0
链接

此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/478555-matrix-problem-for-same-values-of-column#answer_390075

[m,n] = size(A);
B = [(1:m)',A(:,2:3)];
k = B(1,2:3);
ii = 1;
C{1} = [];
while ~isempty(B)
    i0 = ismember(B(:,2:3),k);
    lo = any(i0,2);
    if any(lo)
        C{ii} = [C{ii};[repmat(ii,nnz(lo),1),B(lo,1)]];
        k = B(xor(i0(:,1),i0(:,2)),2:3);
        B = B(~lo,:);
    else
        ii = ii + 1;
        k = B(1,2:3);
        C{ii} = [];
    end
end
iii = cat(1,C{:});
T = array2table(A);
T = T(iii(:,2),:);
T.g = iii(:,1);
T = sortrows(T,{'g','A1'},{'ascend','descend'});
T = rowfun(@(x,y,z)[x(1),y(1),z(1)],T,'GroupingVariables','g');