I would like to extract certain rows from a data frame containing one colum as Date (column C). Here is a small example:

The output should look like this:

```
Before <- data.frame(A=c("0010","0011","0012","0015","0024","0032","0032","0033","0039","0039","0039","0041","0054"),
                     B=c(11,12,11,11,12,12,12,11,"NA","NA",11,11,11),
                     C=c("2014-01-07","2013-06-03","2013-07-29","2014-07-14","2012-12-17","2013-08-21","2013-08-21","2014-07-11","2012-10-06","2012-10-06","2013-10-22","2014-05-28","2014-03-26"))

After <- data.frame(A=c("0010","0011","0012","0015","0024","0032","0033","0039","0041","0054"),
                    B=c(11,12,11,11,12,12,11,11,11,11),
                    C=c("2014-01-07","2013-06-03","2013-07-29","2014-07-14","2012-12-17","2013-08-21","2014-07-11","2013-10-22","2014-05-28","2014-03-26"))

```

So would I'm aiming for is:

1. Only give out entries with the latest date (out of row 9,10,11 (BEFORE)) --> give out only row 8 (AFTER)
2. Give out identical entries only once (row 6 and 7 (BEFORE)) --> give out only row 6 (AFTER)

I wasn't able to find a solution using subset, unique etc. Any help appreciated!