Lee wrote
> Hi,
>
> I am struggling with this issue and need some helps. The data set 'DF'
> includes persons' IDs and other variables A, B, and C. Each Person has
> multiple values in A, B, and C. What I am trying to do is 1) selecting a
> maximum value of B within same ID, and 2) making a new data set (DF.2)
> that select rows aligning with the maximum value of B.
>
> DF and DF.2 are below. I've used functions combining which.max, subset,
> and loop, but it did not work. If you have ideas, please help.
>
>> DF
> ID A B C
> 1 12 36 2
> 1 15 30 2
> 2 56 11 2
> 2 33 30 2
> 3 83 23 2
> 3 58 7 2
> 4 75 2 2
> 4 82 36 2
> 5 77 35 2
> 5 75 23 2
> 6 73 10 2
> 6 76 35 2
> 7 75 14 2
> 7 21 30 2
> 8 14 11 2
> 8 46 11 2
> 8 75 11 2
> 8 30 36 2
> 9 21 35 2
> 9 75 23 2
>
>
> DF.2
> ID A B C
> 1 12 36 2
> 2 33 30 2
> 3 83 23 2
> 4 82 36 2
> 5 77 35 2
> 6 76 35 2
> 7 21 30 2
> 8 30 36 2
> 9 21 35 2
>
> Thank you in advance,
>
> Lee
How about using ddply?
library(plyr)
txt <-"ID A B C
1 12 36 2
1 15 30 2
2 56 11 2
2 33 30 2
3 83 23 2
3 58 7 2
4 75 2 2
4 82 36 2
5 77 35 2
5 75 23 2
6 73 10 2
6 76 35 2
7 75 14 2
7 21 30 2
8 14 11 2
8 46 11 2
8 75 11 2
8 30 36 2
9 21 35 2
9 75 23 2"
d <- read.table(textConnection(txt), header = TRUE)
closeAllConnections()
ddply(d,~ID,function(x){x[which.max(x$B),]})
# Returns
ID A B C
1 1 12 36 2
2 2 33 30 2
3 3 83 23 2
4 4 82 36 2
5 5 77 35 2
6 6 76 35 2
7 7 21 30 2
8 8 30 36 2
9 9 21 35 2
HTH
Pete
--
View this message in context:
http://r.789695.n4.nabble.com/Selecting-a-maximum-value-in-same-ID-tp4686492p4686500.html
Sent from the R help mailing list archive at Nabble.com.
______________________________________________
R-help@r-project.org mailing list
https://stat.ethz.ch/mailman/listinfo/r-help
PLEASE do read the posting guide http://www.R-project.org/posting-guide.html
and provide commented, minimal, self-contained, reproducible code.
