Find element in matrix

Question

Eduardo 2012-4-3

0
链接

此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/34406-find-element-in-matrix

Hello, I have a matrice and i whant to find if there are 2 iqual elements in diferent rows...

In this case i should find the number 1 and 2. But i whant to find one at a time. Can someone help me with this? Thank´s.

1 个评论
显示 -1更早的评论隐藏 -1更早的评论

Image Analyst 2012-4-6

A is comprised on ONLY integers, right? Else you need to consider the FAQ: http://matlab.wikia.com/wiki/FAQ#Why_is_0.3_-_0.2_-_0.1_.28or_similar.29_not_equal_to_zero.3F

请先登录，再进行评论。

请先登录，再回答此问题。

Answer 1

Richard Brown 2012-4-11

1
链接

此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/34406-find-element-in-matrix#answer_44132

在 MATLAB Online 中打开

Here's a slightly uglier way that will work. If you need the code to perform quickly, you'd obviously preallocate your arrays m and z

z = zeros(0, 2);
m = [];
for a = unique(A(:)');
  [I, ~] = find(A == a);
  if numel(I) == 2
    m = [m a];
    z = [z; setdiff(reshape(A(I, :), 1, 4), a)];
  end
end

1 个评论
显示 -1更早的评论隐藏 -1更早的评论

Eduardo 2012-4-16

Thank´s a lot.

请先登录，再进行评论。

Answer 2

Thomas 2012-4-3

1
链接

此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/34406-find-element-in-matrix#answer_43142

在 MATLAB Online 中打开

A =   [1     2
       3     5
       2     4
       6     1 ];
intersect(A(:,1),A(:,2))

1 个评论
显示 -1更早的评论隐藏 -1更早的评论

Sean de Wolski 2012-4-3

or ismember()

请先登录，再进行评论。

Answer 3

Thomas 2012-4-6

1
链接

此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/34406-find-element-in-matrix#answer_43555

在 MATLAB Online 中打开

Try this

clear all

A =   [1     2
       3     5
       2     4
       6     1 ];  
c=intersect(A(:,1),A(:,2));
for i=1:length(c)
[p(:,:),q(:,:)]=find(A==c(i));
l=A(p(:),:);
m=unique(l)';
z(i,:)=m(m~=c(i));
end
c       % common elements 1 and 2
z       % elements associated with  1=2,6 and 2=1,4

Output will be

c =
          1.00
          2.00
z =
          2.00          6.00
          1.00          4.00

1 个评论
显示 -1更早的评论隐藏 -1更早的评论

Eduardo 2012-4-11

First of all, thanks.

It works only in some cases... In the case of the same element be on the same row but diferent lines, with this code can´t be found... Any idea?

请先登录，再进行评论。

Answer 4

Eduardo 2012-4-6

0
链接

此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/34406-find-element-in-matrix#answer_43547

Thank´s... What i need is something more complex, but i didn´t explain it... If i find 2 iqual elements like number 1, for example, what i need to do is connect the other elements in the same line. If i find 1 in to lines ([1 2] and [6 1]) what i need to do is create a new line with [2 6]. I don´t know how to do it...