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

[sjbarry]

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