Inserting a new row to data frame for each group id

Question

I\'ve looked extensively on stack overflow for a solution, but have yet to find one that works for me. I have a data frame that looks something like this:

id         


        

Answer 1

We can do this with data.table. Convert the 'data.frame' to 'data.table' (setDT(df1)), grouped by 'id', get the last row with tail, assign the 'latitude' and 'longitude' with the new values, rbind with the original dataset and order by 'id'.

library(data.table)
rbind(setDT(df1), df1[, tail(.SD, 1) , by = id
        ][, c("latitude", "longitude") := .(394681.4,  6017550)
         ])[order(id)]
#    id  time latitude longitude
#1:  A 11:10 381746.0   6008345
#2:  A 11:11 381726.2   6008294
#3:  A 11:11 394681.4   6017550
#4:  B 10:56 381703.0   6008214
#5:  B 10:57 381679.7   6008134
#6:  B 10:57 394681.4   6017550
#7:  C  4:30 381654.4   6008083
#8:  C  4:31 381629.2   6008033
#9:  C  4:31 394681.4   6017550

---

Or using dplyr, with similar methodology

library(dplyr)
df1 %>%
   group_by(id) %>%
   summarise(time = last(time)) %>%
   mutate(latitude = 394681.4, longitude = 6017550) %>% 
   bind_rows(df1, .) %>% 
   arrange(id)