Find indices of one array in another array.

Question

0 个投票

I have two different sized two column arrays, like the example below:

A = [1 1; 1 2; 2 2; 2 3; 3 3; 3 4; 4 3; 4 4];
B = [1 1; 2 2; 3 3; 4 4];

Now I want to find the indices of the rows in A that are equal to B. So the answer should be:

idx_rows = [1 3 5 8]

How can I do this?

Thanks!

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Answer 1

Birdman 2018-3-28

编辑：Birdman 2018-3-28

0 个投票

[~,idx]=setdiff(A,B,'rows');
idx_rows=setdiff(1:size(A,1),idx)

Answer 2

Stephen23 2018-3-28

编辑：Stephen23 2018-3-28

2 个投票

The simplest solution is to use ismember:

>> A = [1 1; 1 2; 2 2; 2 3; 3 3; 3 4; 4 3; 4 4];
>> B = [1 1; 2 2; 3 3; 4 4];
>> [~,idx] = ismember(B,A,'rows')
idx =
   1
   3
   5
   8