[R] Select rows based on matching conditions and logical operators
kborgmann
borgmann at email.arizona.edu
Wed Jul 25 19:10:04 CEST 2012
Hi,
I have a dataset in which I would like to select rows based on matching
conditions and return the maximum value of a variable else return one row if
duplicate counts exist. My dataset looks like this:
PGID PTID Year Visit Count
6755 53121 2009 1 0
6755 53121 2009 2 0
6755 53121 2009 3 0
6755 53122 2008 1 0
6755 53122 2008 2 0
6755 53122 2008 3 1
6755 53122 2009 1 0
6755 53122 2009 2 1
6755 53122 2009 3 2
I would like to select rows if PTID and Year match and return the maximum
count else return one row if counts are the same, such that I get this
output
PGID PTID Year Visit Count
6755 53121 2009 1 0
6755 53122 2008 3 1
6755 53122 2009 3 2
I tried the following code and the output is almost correct but duplicate
values were included
df2<-with(df, sapply(split(df, list(PTID, Year)),
function(x) if (nrow(x)) x[which(x$Count==max(x$Count)),]))
df<-do.call(rbind,df)
rownames(df)<-1:nrow(df)
Any suggestions?
Thanks much for your responses!
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