unique rows of matrix

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xplore29
xplore29 on 25 Mar 2013
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

Accepted Answer

Matt Kindig
Matt Kindig on 25 Mar 2013
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)?
  1 Comment
xplore29
xplore29 on 25 Mar 2013
I need to create such matrices multiple times. So I was thinking of avoiding this additional step

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More Answers (1)

Matt J
Matt J on 25 Mar 2013
Edited: Matt J on 25 Mar 2013
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.

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