Hi,
This seems to work (although I have this sense that I am missing
something, but I cannot put my finger on it). There are undoubtedly
other ways:
## data in a form ready for copy and pasting (created using dput() )
dat <- structure(list(value = c(4L, 5L, 2L, 10L, 9L, 34L, 100L, 34L,
101L), level = structure(c(1L, 1L, 1L, 2L, 2L, 2L, 3L, 3L, 3L
), .Label = c("A", "B", "C"), class = "factor"), rank = c(2L,
3L, 1L, 2L, 1L, 3L, 2L, 1L, 3L)), row.names = c(NA, -9L), .Names = c("value",
"level", "rank"), class = "data.frame")
## add a variable, 'rank' that does what you want
dat[order(dat$value), "rank"] <- with(dat[order(dat$value), ],
ave(value, level, FUN = seq_along))
HTH,
Josh
On Fri, May 27, 2011 at 12:12 PM, xin wei <xin...@stat.psu.edu> wrote:
> hello, I have the following data manipulation issue. the following is the
> sample data:
>
> value level
> 4 A
> 5 A
> 2 A
> 10 B
> 9 B
> 34 B
> 100 C
> 34 C
> 101 C.
>
> I hope to get the following result:
> value level rank
> 2 A 1
> 4 A 2
> 5 A 3
> 9 B 1
> 10 B 2
> 34 B 3
> 34 C 1
> 100 C 2
> 101 C. 3
>
> as you may see, I need the data sorted and indexed within each level of
> "level". what do I need to do calculate the rank variable?
>
> thanks,
>
> --
> View this message in context:
> http://r.789695.n4.nabble.com/how-to-add-row-index-based-a-categorical-column-tp3556126p3556126.html
> Sent from the R help mailing list archive at Nabble.com.
>
> ______________________________________________
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> PLEASE do read the posting guide http://www.R-project.org/posting-guide.html
> and provide commented, minimal, self-contained, reproducible code.
>
--
Joshua Wiley
Ph.D. Student, Health Psychology
University of California, Los Angeles
http://www.joshuawiley.com/
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