On Sep 20, 2010, at 2:01 PM, David Winsemius wrote:
On Sep 20, 2010, at 1:40 PM, Joshua Wiley wrote:
On Mon, Sep 20, 2010 at 10:27 AM, Phil Spector
<spec...@stat.berkeley.edu> wrote:
Harold -
Two ways that come to mind:
1) do.call(rbind,lapply(split(tmp,tmp$index),function(x)x[1:5,]))
2) subset(tmp,unlist(tapply(foo,index,seq))<=5)
3) do.call(rbind, by(tmp, tmp$index, .Primitive("["), 1:5, 1:2))
I found that rather interesting but somewhat puzzling. I generally
thought that using "[" should "work" but by() was complaining:
Error in FUN(X[[1L]], ...) : could not find function "FUN"
So tried using back-quotes and got a sensible result.
The need for back-quoting disappears if we add a match.fun call to
by.data.frame():
by.data.frame <-
function (data, INDICES, FUN, ..., simplify = TRUE)
{ FUN <- match.fun(FUN)
if (!is.list(INDICES)) {
IND <- vector("list", 1L)
IND[[1L]] <- INDICES
names(IND) <- deparse(substitute(INDICES))[1L]
}
else IND <- INDICES
FUNx <- function(x) FUN(data[x, , drop = FALSE], ...)
nd <- nrow(data)
ans <- eval(substitute(tapply(1L:nd, IND, FUNx, simplify =
simplify)),
data)
attr(ans, "call") <- match.call()
class(ans) <- "by"
ans
}
I would have thought such a call would be in the by.data.frame and
by.default code but they seem to be "missing in action". Would there
be any downside to modifying those functions in that manner?
--
David.
> do.call(rbind, by(tmp, tmp$index, FUN=`[`, 1:5, 1:2))
index foo
1.6 1 -3.0267759
1.7 1 -1.3725536
1.19 1 -1.1476048
1.16 1 -1.0963967
1.2 1 -1.0684793
2.29 2 -1.6601486
2.21 2 -1.2633632
2.22 2 -0.9875626
2.38 2 -0.9515301
2.30 2 -0.8638903
Unlike Dalgaard who arrived at a similar result via a different
route and called the row names "silly", I thought they were
informative. But maybe the sobriquet was directed at his second
solution. I couldn't tell.
--
David.
Josh
- Phil Spector
Statistical Computing
Facility
Department of Statistics
UC Berkeley
spec...@stat.berkeley.edu
On Mon, 20 Sep 2010, Doran, Harold wrote:
Suppose I have a data frame, such as the one below:
tmp <- data.frame(index = gl(2,20), foo = rnorm(40))
And further assume it is sorted by index and then by the variable
foo.
tmp <- tmp[order(tmp$index, tmp$foo) , ]
Now, I want to grab the first N rows of tmp for each index. In
the end,
what I want is the data frame 'result'
tmp1 <- subset(tmp, index == 1)
tmp2 <- subset(tmp, index == 2)
tmp1 <- tmp1[1:5,]
tmp2 <- tmp2[1:5,]
result <- rbind(tmp1, tmp2)
Does anyone see a way to subset and subsequently bind without a
loop?
Harold
[[alternative HTML version deleted]]
______________________________________________
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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.
______________________________________________
R-help@r-project.org mailing list
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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/
______________________________________________
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.
David Winsemius, MD
West Hartford, CT
______________________________________________
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.
David Winsemius, MD
West Hartford, CT
______________________________________________
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.
