Trying to extract the rows from a matrix where the values from the first two columns match the values from another matrix

Question

Michael Bochert 2024-1-31

0
链接

此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/2076791-trying-to-extract-the-rows-from-a-matrix-where-the-values-from-the-first-two-columns-match-the-value

评论： Michael Bochert 2024-1-31

Hi, I am trying to extract the rows from a matrix where the values from the first two columns of that matrix match the values from another matrix.

Basically, if the values in column 1 AND column 2 match the values for column 1 AND column 2 from another matrix, I want to extract the entire row. I want to do this for each row where the values match, essentially making a new matrix of the extracted rows.

Any help would be appreciated! Thanks.

0 个评论
显示 -2更早的评论隐藏 -2更早的评论

请先登录，再进行评论。

请先登录，再回答此问题。

Answer 1

Dyuman Joshi 2024-1-31

在 MATLAB Online 中打开

%Sample data for example
y1 = magic(5)
y1 = 5×5
    17    24     1     8    15
    23     5     7    14    16
     4     6    13    20    22
    10    12    19    21     3
    11    18    25     2     9
y2 = y1;
y2(randi(25,1,5)) = 0
y2 = 5×5
    17     0     1     8    15
     0     5     7    14    16
     0     6    13    20    22
    10    12    19    21     3
    11    18    25     0     0
%Comparison
idx = all(y1(:,1:2)==y2(:,1:2), 2)
idx = 5×1 logical array
   0
   0
   0
   1
   1
out = y1(idx, :)
out = 2×5
    10    12    19    21     3
    11    18    25     2     9

If you are working with floating point numbers, use a tolerance to compare instead of equality

tol = 1e-6;
idx = all(abs(y1(:,1:2)-y2(:,1:2))<tol,2)

3 个评论
显示 1更早的评论隐藏 1更早的评论

Dyuman Joshi 2024-1-31

在 MATLAB Online 中打开

In that case

%Sample data for example
y1 = magic(5)
y1 = 5×5
    17    24     1     8    15
    23     5     7    14    16
     4     6    13    20    22
    10    12    19    21     3
    11    18    25     2     9
y2 = [y1; randi(25, 2, 5)];
k = randi(numel(y2),1,14); 
y2(k) = k*5
y2 = 7×5
    17    24    75     8    15
    10     5    80    14    16
     4    50    13    20    22
    10    55    19   125     3
    11    18    95     2     9
    21    22   100    15   170
    15    70    14   140   175
%Comparison
[idx1,idx2] = ismember(y1(:,1:2),y2(:,1:2),'rows')
idx1 = 5×1 logical array
   1
   0
   0
   0
   1
idx2 = 5×1
     1
     0
     0
     0
     5
out1 = y1(idx1, :)
out1 = 2×5
    17    24     1     8    15
    11    18    25     2     9
out2 = y2(idx2(idx1),:)
out2 = 2×5
    17    24    75     8    15
    11    18    95     2     9