# [Rd] integer coercion when indexing and subsetting (PR#2430)

**maechler@stat.math.ethz.ch
**
maechler@stat.math.ethz.ch

*Wed Jan 8 14:07:04 2003*

At the end of his bug report, Philippe says
PhGr> ..... Moreover, the subset operation [] uses as.integer() and
PhGr> consequently, can suffer from the same syndrome. A WARNING section in
PhGr> Extract.Rd would be welcome too.
[BTW: Thank you Philippe! ]
Currently, "Extract.Rd" does not say anything on the kind of
indices `i' that can be used in things like x[i].
OTOH, the R language reference has a nice section
>>* Indexing by vectors
*>>* -------------------
*>>* R allows some powerful constructions using vectors as indices. We
*>>* shall discuss indexing of simple vectors first. For simplicity, assume
*>>* that the expression is `x[i]'. Then the following possibilities exist
*>>* according to the type of `i'.
*>>*
*>>* *Integer* ...............
*>>* ........................
*>>*
*>>*
*>>* * *Other numeric*. Non-integer values are converted to integer
*>>* before use.
*>>*
*>>* <<........>>
*
I agree with Philippe that help(Extract) should say more.
1) point to the "R Language Reference"
BTW: we should think on how to do this with links that work
with HTML/PDF and also with ESS and Info (I read all R
manuals in info most of the time).
For the moment, just could use \url{....}, right?
2) Tell about `i' = names or integers or as.integer(numeric)
at least, right?
Martin Maechler <maechler@stat.math.ethz.ch> http://stat.ethz.ch/~maechler/
Seminar fuer Statistik, ETH-Zentrum LEO C16 Leonhardstr. 27
ETH (Federal Inst. Technology) 8092 Zurich SWITZERLAND
phone: x-41-1-632-3408 fax: ...-1228 <><