Get rid of rows with duplicate attributes in R

Question

I have a big dataframe with columns such as:

ID, time, OS, IP

Each row of that dataframe corresponds to one entry. Within that dataframe for so

Answer 1

If you want to keep one row for each ID, but there is different data on each row, then you need to decide on some logic to discard the additional rows. For instance:

df <- data.frame(ID=c(1, 2, 2, 3), time=1:4, OS="Linux")
df
  ID time    OS
1  1    1 Linux
2  2    2 Linux
3  2    3 Linux
4  3    4 Linux

Now I will keep the maximum time value and the last OS value:

library(plyr)
unique(ddply(df, .(ID), function(x) data.frame(ID=x[,"ID"], time=max(x$time), OS=tail(x$OS,1))))
  ID time    OS
1  1    1 Linux
2  2    3 Linux
4  3    4 Linux