On 12-01-10 6:04 PM, Eric Rupley wrote:
Hi--
I suspect this is a frequently considered (and possibly asked) question, but I
haven't thus far found an answer:
For slicing a vector with x[…], is there a symbol for length(x)?
No, there isn't. You don't need it much, but if you do you'll have to
calculate it. You'll often save a noticeable amount of execution time
if you store it in a local variable rather than calling length(x)
repeatedly.
Duncan Murdoch
I'm seeking a short-hand for referring to the length of vector one is trying to
index.
E.g., for a data.frame, say,
test.frame<-data.frame(matrix(c(1:100),ncol=10,nrow=10,byrow=T))
names(test.frame)<- names(islands)[1:10]
is there a short-hand for subsetting
test.frame$Baffin[1:(length(test.frame$Baffin)-3)]
[1] 6 16 26 36 46 56 66
that would allow one to avoid the "(length(some.dataframe$variable)-offset)"?
I was thinking something paralleling the use of negative indices in […] might
exist with seq(from,to), e.g. for the above
test.frame$Baffin[seq(,7)]
[1] 6 16 26 36 46 56 66
works. But the fantasy
test.frame$Baffin[seq(,-3)]
obviously doesn't…
Any suggestions will be gratefully appreciated…
As always, many thanks to the patient list members who helps on these simple
questions...
Best,
Eric
--
Eric Rupley
University of Michigan, Museum of Anthropology
1109 Geddes Ave, Rm. 4013
Ann Arbor, MI 48109-1079
erup...@umich.edu
+1.734.276.8572
______________________________________________
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.
______________________________________________
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.
