Hi,
I have a data.frame which is ordered by score, and has a factor column:
Browse[1]> wc[c("report","score")]
report score
9 ADEA 0.96
8 ADEA 0.90
11 Asylum_FED9 0.86
3 ADEA 0.75
14 Asylum_FED9 0.60
5 ADEA 0.56
13 Asylum_FED9 0.51
16 Asylum_FED9 0.51
2 ADEA 0.42
7 ADEA 0.31
17 Asylum_FED9 0.27
1 ADEA 0.17
4 ADEA 0.17
6 ADEA 0.12
10 ADEA 0.11
12 Asylum_FED9 0.10
15 Asylum_FED9 0.09
18 Asylum_FED9 0.07
Browse[1]>
I need to add a column indicating rank within each factor group, which I
currently accomplish like so:
wc$rank <- 0
for(report in as.character(unique(wc$report))) {
wc[wc$report==report,]$rank <- 1:sum(wc$report==report)
}
I have to wonder whether there's a better way, something that gets rid of
the for() loop using tapply() or by() or similar. But I haven't come up
with anything.
I've tried these:
by(wc, wc$report, FUN=function(pr){pr$rank <- 1:nrow(pr)})
by(wc, wc$report, FUN=function(pr){wc[wc$report %in% pr$report,]$rank <-
1:nrow(pr)})
But in both cases the effect of the assignment is lost, there's no $rank
column generated for wc.
Any suggestions?
-Ken
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