Bernard,
Thanks, but I can't take that shortcut.
The data is an xts object, and I may not want to order every group. So, I need
a way to just order one group at a time.
Thoughts?
--
Noah Silverman
UCLA Department of Statistics
8208 Math Sciences Building
Los Angeles, CA 90095
On May 12, 2012, at 11:38 AM, Berend Hasselman wrote:
>
> On 12-05-2012, at 20:04, Noah Silverman wrote:
>
>> Is there a way to order data and subset it at the same time??
>>
>>
>>
>> I want to sort all the members of group A by their values in column 3. (I'll
>> then do the same for each subsequent group.) This could be done in a loop
>> building up another vector, but I like to avoid loops in R.
>> -------------------------------------
>> a <- temp[temp$group=="A",]
>> a <- a[order(a[,3]),]
>> temp[temp$group=="A",] <- a
>> ------------------------------------------
>>
>> Iid like to do this in a single step for each group. However, I can't
>> figure out how to order and subset at the same time.
>>
>> This *does not work* but should illustrate what I'm trying to do
>>
>> temp[temp$group=="A",] <- temp[ temp$group=="A" &
>> order(temp[temp$group=="A",3]) , ]
>>
>>
>> Suggestions?
>
> set.seed(413)
>
> temp <- data.frame(group=rep(c("A","B","C"), rep=5),
> tt=1:15,val=round(runif(15),2), stringsAsFactors=FALSE)
> idx <- order(temp$group,temp$val)
> # or idx <- order(temp[,1],temp[,3])
> idx
> z2 <- temp[idx,]
> rownames(z2) <- NULL
> z2
>
> Possible NA's etc. not taken into account.
>
> Berend
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