matlab - 如何删除矩阵中的特定行

Question

我有一个矩阵 A ，我想删除具有相似值的行 (1,1), (2,2), (3 ,3)

A =
     1     1
     2     1
     3     1
     1     2
     2     2
     1     3
     3     3

所以矩阵应该是这样的

 2     1
 3     1
 1     2
 1     3

Answer 1

另一种不调用任何函数的方法:

 A = A(A(:,1) == A(:,2),:)

此方法与基于diff() 的解决方案的效率:

n = 10;
y = [round(rand(n,1)) round(rand(n,1))];

tic;
for i = 1:1e4
  A = y;
  A(diff(A,[],2)~=0,:);
end
toc
Elapsed time is 0.091990 seconds.

tic;
for i = 1:1e4
  A = y;
  A = A(A(:,1) == A(:,2),:);
end
toc
Elapsed time is 0.037842 seconds.



% Suggestion of @Dan in the comments
tic;
for i = 1:1e4
  A = y;
  A(A(:,1) == A(:,2),:) = [];
end
toc
Elapsed time is 0.147636 seconds.