Please provide commented, minimal, self-contained, reproducible code, or at least a before/after of what you data would look like. Taking a guess at what you are asking, here is one way of doing it:
> x <- data.frame(cat=sample(LETTERS[1:3],20,TRUE),a=1:20, b=runif(20)) > x cat a b 1 B 1 0.65472393 2 C 2 0.35319727 3 B 3 0.27026015 4 A 4 0.99268406 5 C 5 0.63349326 6 A 6 0.21320814 7 C 7 0.12937235 8 A 8 0.47811803 9 A 9 0.92407447 10 A 10 0.59876097 11 A 11 0.97617069 12 A 12 0.73179251 13 B 13 0.35672691 14 C 14 0.43147369 15 C 15 0.14821156 16 C 16 0.01307758 17 B 17 0.71556607 18 B 18 0.10318424 19 C 19 0.44628435 20 B 20 0.64010105 > # create a list of the indices of the data grouped by 'cat' > split(seq(nrow(x)), x$cat) $A [1] 4 6 8 9 10 11 12 $B [1] 1 3 13 17 18 20 $C [1] 2 5 7 14 15 16 19 > # or do you want the data > split(x, x$cat) $A cat a b 4 A 4 0.9926841 6 A 6 0.2132081 8 A 8 0.4781180 9 A 9 0.9240745 10 A 10 0.5987610 11 A 11 0.9761707 12 A 12 0.7317925 $B cat a b 1 B 1 0.6547239 3 B 3 0.2702601 13 B 13 0.3567269 17 B 17 0.7155661 18 B 18 0.1031842 20 B 20 0.6401010 $C cat a b 2 C 2 0.35319727 5 C 5 0.63349326 7 C 7 0.12937235 14 C 14 0.43147369 15 C 15 0.14821156 16 C 16 0.01307758 19 C 19 0.44628435 On Sat, Jul 12, 2008 at 3:32 AM, <[EMAIL PROTECTED]> wrote: > I have search the archive and I could not find what I need so I will try to > ask the question here. > > I read a table in (read.table) > > a <- read.table(.....) > > The table has column names like DayOfYear, Quantity, and Category. > > The values in the row for Category are strings (characters). > > I want to get all of the rows grouped by Category. The number of unique > category names could be around 50. Say for argument sake the number of > categories is exactly 50. Can I somehow get a vector of length 50 containing > the rows corresponding to the category (another vector)? I realize I can > access any row a[i]$Category (right?). But I wanta vector containing the rows > corresponding to each distinct Category name. > > Thank you. > > Kevin > > ______________________________________________ > 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. > -- Jim Holtman Cincinnati, OH +1 513 646 9390 What is the problem you are trying to solve? ______________________________________________ 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.
