MATLAB: Remove duplicate rows based on subset of row elements

Question

Hello everyone,

I tried to find a similar problem – relatively simple I believe – but I could not find a solution. If, for instrance, I have a matrix such as

A = [1 1 1 100; 2 2 2 200; 3 3 3 300; 1 1 1 500]

how can I remove from A the fourth row based on the fact that only the thee first elements of the that row are identical to the three elmenets in the first row?

Also, what if I have

A = [1 1 1 100; 2 2 2 200; 3 3 3 300; 1 1 1 500; 1 1 1 600]

and, again, I just want to keep the first row?

Thank you for your help.

Answer 1

A(unique(A(1:3),'rows'),:)