Finding the last entry

 Let's say we have a table like below. The same product run on the same machine more than one time, re-work or re-processed.

What we are interested in the last run. 

Using base command aggregate 

laste_entry_max <- aggregate(RUN_Number ~ ID, last_entry, max)

By doing a merge you can do the subset the table.

laste_entry_max_all_c <- merge(laste_entry_max, last_entry, by = c('ID', 'RUN_Number'), all.x = T) 

If the run number information is not there we can use Time_Stamp

You can also use dplyr package

library(dplyr) 

laste_entry_max <- last_entry %>%  

                      group_by(ID) %>% 

                          slice(which.max(RUN_Number))