Is this the result you are after, where the event number
(within a group) are sorted according to the event/prev_event
pairs (prev_event in a row matches event of the previous row)?
> ave(d, d$group, FUN=function(z) z[ match(tsort(z$prev_event, z$event)[-1],
> z$event), ])
event prev_event group
1 845 0 5360
2 234 845 5360
3 993 234 5360
4 153 993 5360
5 926 153 5360
6 848 926 5360
7 234 0 8765
8 968 234 8765
9 545 968 8765
10 625 111 3334
11 713 625 3334
12 227 713 3334
13 181 227 3334
14 744 181 3334
15 913 0 2329
16 355 913 2329
17 761 355 2329
18 324 761 2329
19 119 324 2329
20 372 119 2329
21 890 372 2329
22 189 890 2329
23 719 189 2329
24 266 719 2329
'tsort' is a topological sorting function, like
the Unix tsort. It is overkill for this application
(and probably could be faster and do some more
error checking) but I had it hanging around:
tsort <- function (before, after)
{
# topological sort: Kahn's 1962 algorithm, from Wikipedia
# before and after should be equal-length vectors of the
# same type.
L <- before[0]
S <- setdiff(before, after)
while (length(S) > 0) {
n <- S[1]
S <- S[-1]
L[length(L) + 1] <- n
m <- after[e <- before == n]
after <- after[!e]
before <- before[!e]
S <- c(S, m[!is.element(m, after)])
}
if (length(after) > 0) {
stop("Graph contains a cycle")
}
else {
L
}
}
Your data was
d <- data.frame(
event = c(845, 926, 993, 234, 848, 153, 234, 968, 545, 625, 744, 181,
713, 227, 913, 372, 719, 119, 761, 890, 266, 324, 189, 355),
prev_event = c(0, 153, 234, 845, 926, 993, 0, 234, 968, 111, 181, 227, 625,
713, 0, 119, 189, 324, 355, 372, 719, 761, 890, 913),
group = c(5360, 5360, 5360, 5360, 5360, 5360, 8765, 8765, 8765, 3334,
3334, 3334, 3334, 3334, 2329, 2329, 2329, 2329, 2329, 2329, 2329,
2329, 2329, 2329))
Bill Dunlap
Spotfire, TIBCO Software
wdunlap tibco.com
> -----Original Message-----
> From: r-help-boun...@r-project.org [mailto:r-help-boun...@r-project.org] On
> Behalf Of Sally Zhen
> Sent: Wednesday, October 12, 2011 7:56 AM
> To: r-help@r-project.org
> Subject: [R] loop function within a loop
>
> 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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and provide commented, minimal, self-contained, reproducible code.
