# Re: [R] sorting a data.frame by mean values of grouped data

From: Mark W Kimpel <mwkimpel_at_gmail.com>
Date: Thu, 13 Mar 2008 01:06:22 -0400

Stephen,

I am sure someone will have a more elegant solution, but the following works. Mark

d.lst <- split(x = d, f = as.factor(d\$Group), drop = FALSE) d.lst.mn <- sapply(d.lst, FUN =
function(x){mean(as.numeric(as.character(x\$Value)))}) o <- order(d.lst.mn, decreasing = TRUE)
d.lst.mn <- d.lst.mn[o]

e <- NULL
for (i in 1:length(d.lst.mn)){

if (i == 1){
e <- d[d\$Group == names(d.lst.mn)[i],]    } else {
e <- rbind(e, d[as.character(d\$Group) == names(d.lst.mn)[i],])    }
}
e

Mark W. Kimpel MD ** Neuroinformatics ** Dept. of Psychiatry Indiana University School of Medicine

15032 Hunter Court, Westfield, IN 46074

(317) 490-5129 Work, & Mobile & VoiceMail (317) 204-4202 Home (no voice mail please)

mwkimpel<at>gmail<dot>com

sjbarry wrote:
> Hi,
>
> I have what I think is a fairly straightforward problem. I've looked
> through the FAQ's and mailing lists but have been unable to identify a
> solution, probably because I don't understand the language well enough.
>
> I have a set of data d, with 3 columns as shown,
> I want to sort the data Group, mean(Value by Label). I know that this
> can be done for one level, say Label, using factor() but I cannot see
> how to extend that. I have included the code to create the data.frame
> below and would greatly appreciate a solution or a link to a similar
> problem that has already been solved in the mailing list.
> Value Label Group
> 19 Big A
> 29 Big A
> 39 Big A
> 55 Small D
> 33 Small D
> 11 Small D
> 55 Small D
> 66 Small D
> 11 Small D
> 2 Big C
> 3 Big C
> 3 Big C
> 3 Big C
> 3 Big C
> 3 Big C
> 3 Big C
> 3 Small B
> 2 Small B
> 5 Small B
> 6 Small B
> 5 Small B
> 6 Small B
>
> Value <- c(19,29,39,55,33,11,55,66,11,2,3,3,3,3,3,3,3,2,5,6,5,6)
> Group <- c("A","A","A","D","D","D","D","D","D",
> "C","C","C","C","C","C","C","B","B","B","B","B","B")
> Label <- c("Big","Big","Big",
> "Small","Small","Small","Small","Small","Small",
> "Big","Big","Big","Big","Big","Big","Big",
> "Small","Small","Small","Small","Small","Small")
> d <- as.data.frame(cbind(Value, Label, Group))
>
>
> Thanks
>
> Stephen Barry
>

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