On Oct 13, 2010, at 2:19 PM, Jon Zadra wrote:
Hi,
I've looked all over for a solution to this, but haven't had much
look in specifying what I want to do with appropriate search terms.
Thus I'm turning to R-help.
In the process of trying to write a simple function to rename
individual column names in a data frame, I ran into the following
problem: When I rename the columns within my function, I can't seem
to get it to apply to the data frame in the global environment in a
simple manner.
There already is a function (or perhaps a composition of two
functions) that does what you ask. It's the '<-' method for names()
usually invoked in its dyadic form:
names(object) <- character_vector
> df <- data.frame(one=rnorm(10), two=rnorm(10))
> names(df) <- c("three", "four")
> names(df)
[1] "three" "four"
In your case it would work like this:
> names(tempdf)[ which(names(tempdf)=="a") ] <- "g"
> names(tempdf)
[1] "g" "b"
--
David.
Given:
tempdf <- data.frame("a" = 1:6, "b" = 7:12)
#I can rename a to g this way:
names(tempdf)[names(tempdf)=="a"] <- "g"
#Wanting to simplify this for the future, I have the function:
colrename <- function(dframe, oldname, newname) {
names(dframe)[names(dframe)==oldname] <- newname
}
colrename(tempdf, "a", "g")
#However of course the change to tempdf stays within colrename(). I
could add "return(names(dframe))" to the function and then call the
function like:
#names(tempdf) <- colrename(tempdf, "a", "g")
#but at that point its not much simpler than the original:
#names(tempdf)[names(tempdf)=="a"] <- "g"
So, i'm wondering, is there a way to write code within that function
so that the tempdf in the global environment gets changed?
I thought of doing "names(dframe)[names(dframe)==oldname] <<-
newname" but then of course it doesn't replace "dframe" with
"tempdf" in the evaluation, so it seems to be a problem of looking
at some variables within the function environment but others in the
parent environment.
Any help is greatly appreciated.
Thanks,
Jon
--
Jon Zadra
Department of Psychology
University of Virginia
P.O. Box 400400
Charlottesville VA 22904
(434) 982-4744
email: za...@virginia.edu
<http://www.google.com/calendar/embed?src=jzadra%40gmail.com>
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