Comparing arrays and getting the index of extra rows

Question

Pelajar UM 2021-11-2

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https://ww2.mathworks.cn/matlabcentral/answers/1577220-comparing-arrays-and-getting-the-index-of-extra-rows

评论： Pelajar UM 2021-11-2

There are two arrays: A with 8916x3 and B with 6571x3. Each 1x3 set represents xyz coordinates. Array A has some extra coordinates/rows.

I want to compare xyz row by row, and return the index of rows in A that do not exist in B. Then use this index to remove the corresponding extra data from array C (basically C is 8916x3 and it has to be 6571x3 same as B, while keeping the order of rows).

Here's my code but I ge this error: "too many outputs"

[logic,index] =not(ismember(A,B,'rows'))
C(index,:) = [];

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Answer 1

DGM 2021-11-2

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https://ww2.mathworks.cn/matlabcentral/answers/1577220-comparing-arrays-and-getting-the-index-of-extra-rows#answer_822115

Consider:

% example arrays
B = randi(99,5,3)
B = 5×3
    78    21    35
    61    79    55
    47    76     4
    33    86    80
    72    26    38
A = [B; randi(99,3,3)];
A = A(randperm(size(A,1)),:)
A = 8×3
    78    21    35
    61    79    55
    10    40    11
    55    76    42
    50    65    26
    72    26    38
    47    76     4
    33    86    80
% i'm assuming C is some separate array?
C = rand(size(A))
C = 8×3
    0.5299    0.1604    0.0717
    0.6433    0.3189    0.3384
    0.6323    0.7470    0.2365
    0.1172    0.1725    0.8113
    0.3856    0.8772    0.6111
    0.0621    0.1053    0.8808
    0.9019    0.1290    0.7942
    0.0757    0.7127    0.5547
% extract rows from C where A is a member of B, preserving order
C = C(ismember(A,B,'rows'),:)
C = 5×3
    0.5299    0.1604    0.0717
    0.6433    0.3189    0.3384
    0.0621    0.1053    0.8808
    0.9019    0.1290    0.7942
    0.0757    0.7127    0.5547