How to identify duplicate rows in a matrix?

I have a matrix like the below. It could have millions of rows.

A = [Year, Month, Day, Time,   Lon,  Lat,  A,  B,  C;
     2005,  3,     7, 11:30am, -120, 39.5, 20, 31, 5;
     ...
     ... ];

What I want to do is to identify rows with duplicates defined as:

Time = datenum(Year, Month, Day) + Time/24;
Time1 - Time2 < (1/24/60)*30  % less than 30 mins
Lon1 - Lon2   < 0.5
Lat2 - Lat2   < 0.5

For each identified duplicate pair (e.g., Row 15 and Row 6000 are duplicates), I would hope to have two rows in a new matrix:

Year1, Month1, Day1, ... (Row #15)
Year2, Month2, Day2, ... (Row #6000)

Many thanks for any tips!

Answer 1

[Image Analyst]

Try the unique() function. After finding unique rows, then you might want to use the setdiff() function. If you still have trouble, attach a short version of your A with some duplicate rows so people can do it for you.

[Leon]

Many thanks!