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

From: sjbarry <sjb78_at_uow.edu.au>
Date: Thu, 13 Mar 2008 17:19:01 +1100

Thanks Mark,

I see that I made an error in my original request for help. I got my labels and groups mixed up (see below). Nonetheless, your code has been a good pointer in the direction of a solution. I'll post it up when I have it working.

Thanks again,
Stephen Barry.

I should have written it more like this: Given data.frame:

Value Group Label

```     55     D Small
33     D Small
11     D Small
55     D Small
66     D Small
11     D Small
19     A   Big
29     A   Big
39     A   Big
3     B Small
2     B Small
5     B Small
6     B Small
5     B Small
6     B Small
2     C   Big
3     C   Big
3     C   Big
3     C   Big
3     C   Big
3     C   Big
3     C   Big
```

end up with:

Value Group Label

```    19     A   Big
29     A   Big
39     A   Big
2     C   Big
3     C   Big
3     C   Big
3     C   Big
3     C   Big
3     C   Big
3     C   Big
55     D Small
33     D Small
11     D Small
55     D Small
66     D Small
11     D Small
3     B Small
2     B Small
5     B Small
6     B Small
5     B Small
6     B Small

```

>

Mark W Kimpel wrote:
> 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
>>

```--
Stephen Barry
School of Earth and Environmental Sciences
University of Wollongong
Northfields Ave.
Wollongong, NSW. 2522
Australia

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