Suppose I have a dataframe defined as
L3 <- LETTERS[1:3]
(d <- data.frame(cbind(x = 1, y = 1:10), fac = sample(L3, 10, replace
= TRUE)))
x y fac
1 1 1 C
2 1 2 A
3 1 3 B
4 1 4 C
5 1 5 B
6 1 6 B
7 1 7 A
8 1 8 A
9 1 9 B
10 1 10 A
I want to extract those rows that are the first occurrences for each level
of factor 'fac', which are basically the first three rows above. How can
I
achieve that? The real dataframe is more complicated than the example
above, and I can't simply list all the levels of factor 'fac' by
exhaustibly listing all the levels like the following
d[d$fac=='A' | d$fac=='B' | d$fac=='C', ]
Thanks,
Gang
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Hi, Try: ?d[match(unique(d$fac),d$fac),] A.K. On Friday, December 13, 2013 4:17 PM, Gang Chen <gangchen6 at gmail.com> wrote: Suppose I have a dataframe defined as ? ? L3 <- LETTERS[1:3] ? ? (d <- data.frame(cbind(x = 1, y = 1:10), fac = sample(L3, 10, replace = TRUE))) ? x? y fac 1? 1? 1? C 2? 1? 2? A 3? 1? 3? B 4? 1? 4? C 5? 1? 5? B 6? 1? 6? B 7? 1? 7? A 8? 1? 8? A 9? 1? 9? B 10 1 10? A I want to extract those rows that are the first occurrences for each level of factor 'fac', which are basically the first three rows above. How can I achieve that? The real dataframe is more complicated than the example above, and I can't simply list all the levels of factor 'fac' by exhaustibly listing all the levels like the following d[d$fac=='A' | d$fac=='B' | d$fac=='C', ] Thanks, Gang ??? [[alternative HTML version deleted]] ______________________________________________ R-help at 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.
Perfect! Thanks a lot, A.K! On Fri, Dec 13, 2013 at 4:21 PM, arun <smartpink111@yahoo.com> wrote:> > > Hi, > Try: > d[match(unique(d$fac),d$fac),] > A.K. > > > On Friday, December 13, 2013 4:17 PM, Gang Chen <gangchen6@gmail.com> > wrote: > Suppose I have a dataframe defined as > > L3 <- LETTERS[1:3] > (d <- data.frame(cbind(x = 1, y = 1:10), fac = sample(L3, 10, replace > = TRUE))) > > x y fac > 1 1 1 C > 2 1 2 A > 3 1 3 B > 4 1 4 C > 5 1 5 B > 6 1 6 B > 7 1 7 A > 8 1 8 A > 9 1 9 B > 10 1 10 A > > I want to extract those rows that are the first occurrences for each level > of factor 'fac', which are basically the first three rows above. How can I > achieve that? The real dataframe is more complicated than the example > above, and I can't simply list all the levels of factor 'fac' by > exhaustibly listing all the levels like the following > > d[d$fac=='A' | d$fac=='B' | d$fac=='C', ] > > Thanks, > Gang > > [[alternative HTML version deleted]] > > ______________________________________________ > R-help@r-project.org mailing list > https://stat.ethz.ch/mailman/listinfo/r-help > PLEASE do read the posting guide > http://www.R-project.org/posting-guide.html > and provide commented, minimal, self-contained, reproducible code. > >[[alternative HTML version deleted]]
What about: lapply(levels(d$fac), function(x)head(d[d$fac == x,], 1)) Thanks for the reproducible example. If you put set.seed(123) before the call to sample, then everyone who tries it will get the same data frame d. Sarah On Fri, Dec 13, 2013 at 4:15 PM, Gang Chen <gangchen6 at gmail.com> wrote:> Suppose I have a dataframe defined as > > L3 <- LETTERS[1:3] > (d <- data.frame(cbind(x = 1, y = 1:10), fac = sample(L3, 10, replace > = TRUE))) > > x y fac > 1 1 1 C > 2 1 2 A > 3 1 3 B > 4 1 4 C > 5 1 5 B > 6 1 6 B > 7 1 7 A > 8 1 8 A > 9 1 9 B > 10 1 10 A > > I want to extract those rows that are the first occurrences for each level > of factor 'fac', which are basically the first three rows above. How can I > achieve that? The real dataframe is more complicated than the example > above, and I can't simply list all the levels of factor 'fac' by > exhaustibly listing all the levels like the following > > d[d$fac=='A' | d$fac=='B' | d$fac=='C', ] > > Thanks, > Gang-- Sarah Goslee http://www.functionaldiversity.org