Find certain row out of many rows with the same id

I have a matrix whose each row consists of an id column and some other columns with other features of each object. One of the characteristics is a date. Now, some rows of the matrix have the same id and I want to keep only the one with the most recent date. For example, in the table above, the id is in the third column, so, from the second and third row I want to keep only the third, as it has the most recent date. How could I do that in a matrix with many subsets of rows with the same id?

490            673             9987       {'2015-09-10 00:00:00'}           58                      
491         110556            10233       {'2010-02-22 00:00:00'}           70                  
492         110556            10233       {'2011-02-22 00:00:00'}           65                    

Answer 1

[Walter Roberson]

One approach:

sortrows() on the ID column, and the date column in descending order. unique() the ID column with 'stable' and take the second output. Use that to index the sortrows output to get just the first (newest because descending order) entry for each ID.

If necessary re-sort on the first column.

Or...

findgroups() on the ID, and splitapply() specifying a function that will receive the variable entries that are associated with a single ID. The function would datetime() and max() to get the index of the maximum and return that entry from the variables.