It's better to avoid loop in this situation. If you want to reorder
subsets of the data based on event, the follow works
df<-read.table('clipboard',header=TRUE)
sp.or<-lapply(split(df,df$group),function(ldf) ldf[order(ldf$event),])
new.df<-do.call('rbind',sp.or)
Weidong Gu
On Wed, Oct 12, 2011 at 10:55 AM, Sally Zhen <salil...@gmail.com> wrote:
> Hi all,
>
> I'm working on a loop function for a large dataset which contains 1000
> different groups. I would like to reconstruct the order of events within
> each group by using a loop function in R. (Currently the order of events are
> based on the ascending order of prev_event within the group)
>
>
> A demo data frame:
>
> event prev_event group
> 845 0 5360
> 926 153 5360
> 993 234 5360
> 234 845 5360
> 848 926 5360
> 153 993 5360
> 234 0 8765
> 968 234 8765
> 545 968 8765
> 625 111 3334
> 744 181 3334
> 181 227 3334
> 713 625 3334
> 227 713 3334
> 913 0 2329
> 372 119 2329
> 719 189 2329
> 119 324 2329
> 761 355 2329
> 890 372 2329
> 266 719 2329
> 324 761 2329
> 189 890 2329
> 355 913 2329
>
>
> Below is what I have written:
>
> ordering <- vector("list", length(unique(mydata$group)))
> for (j in 1:length(unique(mydata$group))){
> group.j <- mydata[mydata$group == unique(mydata$group)[j], ]
> ordering.j <- c()
> ordering.j[1] <- ifelse(group.j[1, ]$prev_event == 0, group.j[1, ]$event,
> group.j[1, ]$prev_event)
> for (i in 2:nrow(group.j)){
> ordering.j[i] <- group.j[group.j$prev_event == ordering.j[i-1], ]$event}
> ordering[j] <- ordering.j}
> ordering
>
> What I got is:
> Error in ordering.j[i] <- group.j[group.j$prev_event == ordering.j[i - :
> replacement has length zero
>> ordering
> [[1]]
> NULL
>
> [[2]]
> NULL
>
> [[3]]
> NULL
>
>
> However, when I accidentally put a typo in the loop function, instead of
> ordering.j[i] <- group.j[group.j$prev_event == ordering.j[i-1], ]$event},
> I put
> ordering.j[i] <- group.j[group.j$prev_event == ordering.j[i-1],
> ]$prev_event},
> The output is a list of 1000 entries, each with the first event within the
> group, and I received the following warning messages:
> [[1]]
> [1] 1.000680e+17
>
> [[2]]
> [1] 1.001390e+17
>
> [[3]]
> [1] 1.001450e+17
>
> 49: In ordering[j] <- ordering.j :
> number of items to replace is not a multiple of replacement length
> 50: In ordering.j[i] <- group.j[group.j$prev_event == ... :
> number of items to replace is not a multiple of replacement length
>
>
> Why is this happening, and how can I fix it? Any pointer will be greatly
> appreciated!
>
> [[alternative HTML version deleted]]
>
> ______________________________________________
> R-help@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.
>
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