MATLAB: How to find a vector in a matrix without using cycles

Question

Good afternoon. The reason for my message is to ask for help with this problem. Let's say I have a matrix "called A" with 2 columns and -n- number of rows, and I need to look for a vector "B" (which is 1 row and 2 columns) within all the rows that make up "A". You must find the vector in a way that recognizes in a sense or in the opposite sense, then I show an example to better understand what I say.

A =

1 2

3 4

5 3

3 1

6 4

4 2

B=

4 6 ——————-> The vector B can also be inverted (6 4).

The result I expect to be told in which row is the vector "B" inside the matrix "A". for the example above I would expect the answer to be row 5

Thank you very much for your help.

Answer 1

Try this:

A = [1     2
     3     4
     5     3
     3     1
     6     4
     4     2];
 
B = [4    6];
Lidx = ismember(sort(A,2),sort(B,2),'rows')
rowNumber = find(Lidx)

producing:

Lidx =
  6×1 logical array
   0
   0
   0
   0
   1
   0
rowNumber =
     5