Thanks for this, and all the other responses - I have a better
understanding now.
David Winsemius wrote:
On May 30, 2010, at 1:43 AM, i...@whywouldwe.com wrote:
Hi
The docs for R are very practical, which is quite refreshing compared
to other languages, however I can't find any details about all the
things I can do with a vector. I'm expecting methods like
vector.contains('foo') and vector.remove('foo'), maybe those methods
don't exist but I'd love to find a page that details the ones that do.
Since vectors may contain named elements, your request is ambiguous. I
cannot tell whether "foo" is a name or a value. It's also ambiguous
because it's not clear what vector.contains() is supposed to return.
If you read the introductory material, you should find that the
function "[" is fairly fundamental to R operations.
?"["
?which
?grep
> x <- c(foo=3,bar=4)
> x
foo bar
3 4
> x["foo"]
foo
3
> x[-"foo"]
Error in -"foo" : invalid argument to unary operator
# the negation operation on indices only works with numeric arguments
# grep and which provide numeric resutls that can be used for "removal".
> x[grep("foo", names(x))]
foo
3
> x[-grep("foo", names(x))]
bar
4
> x[which(names(x)=="foo")]
foo
3
Minus operations on numeric indices perform removal, at least to the
extent of what is returned, but indexing does not do destructive
removal unless accompanied by "<-" . In fact "[<-" is a function in
its own right.
I'd also like to find some docs about foreach loops (unless there's a
better way to iterate through a vector), I've only found mailing list
posts.
Indexed solution are preferred, so see above, but if you want to find
the help page for the "for" function
?"Control"
--
David Winsemius, MD
West Hartford, CT
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