Wacek Kusnierczyk wrote:
Tony Plate wrote:
Wacek Kusnierczyk wrote:
[snip]
i just can't get it why the manual does not manifestly explain what
'names<-' does, and leaves you doing the guesswork you suggest.
I'm having trouble understanding the point of this discussion.
Someone is calling a replacement function in a way that it's not meant
to be used, and is them complaining about it not doing what he thinks
it should, or about the documentation not describing what happens when
one does that?
where is it written that the function is not meant to be used this way?
you get an example in the man page, showing precisely how it could be
used that way. it also explains the value of 'names<-':
"
For 'names<-', the updated object. (Note that the value of
'names(x) <- value' is that of the assignment, 'value', not the
return value from the left-hand side.)
"
it does speak of 'names<-' used in prefix form, and does not do it in
any negative (discouraging) way.
Is there anything incorrect or missing in the help page for normal
usage of the replacement function for 'names'? (i.e., when used in an
expression like 'names(x) <- ...')
what is missing here in the first place is a specification of what
'normal' means. as far as i can see from the man page, 'normal' does
not exclude prefix use. and if so, what is missing in the help page is
a clear statement what an application of 'names<-' will do, in the sense
of what a user may observe.
Fair enough. I looked at the help page for "names" after sending my
email, and was surprised to see the following in the "DETAILS" section:
"It is possible to update just part of the names attribute via the
general rules: see the examples. This works because the expression there
is evaluated as |z <- "names<-"(z, "[<-"(names(z), 3, "c2"))|. "
To me, this paragraph is far more confusing than enlightening,
especially as also gives the impression that it's OK to use a
replacement function in a functional form. In my own personal opinion
it would be a enhancement to remove that example from the documentation,
and just say you can do things like 'names(x)[2:3] <- c("a","b")'.
I often use name replacement functions in a functional way, and because
one can't use 'names<-' etc in this way, I define my own functions like
the following:
set.names <- function(n,x) {names(x) <- n; x}
(and similarly for set.rownames(), set colnames(), etc.)
I would highly recommend you do this rather than try to use a call like
"names<-"(x, ...).
-- Tony Plate
(I guess that if on the label of fridge there is a picture of a guy
carrying it on his back, then Mr. Fridge-Racer might have some grounds
for suing.)
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