unique rows of matrix

I have to create new matrix A from a given matrix B in the following manner

B=[1 4 2;1 5 2;1 5 2;3 3 4;3 1 4;2 1 3;2 6 3]

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

i-e in forming A we ignore the values which 2nd column takes in and considers only column 1 and 3 create A.

unique(A,'rows') will not do the job . Do I have to create an intermediate matrix from column 1 and 3 and the apply this unique function to get the desired matrix or is there any other option available which avoids formulation of intermediate matrix

Answer 1

[Matt Kindig]

You can easily perform the task using:

A = unique( B(:,[1 3]), 'rows');

But of course, this forms the intermediate matrix to run the unique() function. Is there a particular reason you need to avoid this intermediate matrix running (memory issues, perhaps)?

[xplore29]

I need to create such matrices multiple times. So I was thinking of avoiding this additional step

Answer 2

[Matt J]

You have to create an intermediate matrix, but you don't have to assign it to a variable.

A = unique(B(:,[1 3]),'rows')

What issue do you have with the above? Your B matrix is too small for this to matter and super-large matrices will be painful for UNIQUE anyway.