[R] Vector docs

[info at whywouldwe.com]

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, info at 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
>
>