Yet another way to do this with base R:
dat = read.csv(textConnection('ID, year, score
+ tom, 1995, 88
+ rick, 1994, 90
+ mary, 2000, 97
+ tom, 1998, 60
+ mary, 1998,100'))
do.call(rbind,lapply(split(dat,dat$ID),function(x)x[which.max(x$score),]))
ID year score
mary mary 1998 100
rick rick 1994 90
tom tom 1995 88
- Phil Spector
Statistical Computing Facility
Department of Statistics
UC Berkeley
spec...@stat.berkeley.edu
On Tue, 9 Mar 2010, Tan, Richard wrote:
Hi, I have a data frame with 3 columns: ID, year and score. How can I
select for each unique ID, the year that has the max score? For
example, for data frame
ID, year, score
tom, 1995, 88
rick, 1994, 90
mary, 2000, 97
tom, 1998, 60
mary, 1998,100
I shall have
ID, year, score
tom, 1995, 88
rick, 1994, 90
mary, 1998,100
Thanks,
Richard
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