[R] Select rows based on matching conditions and logical operators

[Rui Barradas]

Hello,

Apart from the output order this does it.
(I have changed 'df' to 'df1', 'df' is an R function, the F distribution 
density.)


df1 <- read.table(text="
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", header=TRUE)


df2 <- with(df1, sapply(split(df1, list(PTID, Year)),
     function(x) if (nrow(x)) x[which.max(x$Count), ]))
df2 <- do.call(rbind, df2)
rownames(df2) <- 1:nrow(df2)
df2

which.max(9, not which().

Hope this helps,

Rui Barradas
Em 25-07-2012 18:10, kborgmann escreveu:
> 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!
>
>
>
>
> --
> View this message in context: http://r.789695.n4.nabble.com/Select-rows-based-on-matching-conditions-and-logical-operators-tp4637809.html
> Sent from the R help mailing list archive at Nabble.com.
>
> ______________________________________________
> R-help at 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.