Very sorry to hear this bit you. If you need a copy of names before
changing them by reference :
oldnames <- copy(names(DT))
This will be documented and it's on the bug list to do so. copy is
needed in other circumstances too, see ?copy.
More details here :
http://stackoverflow.com/questions/18662715/colnames-being-dropped-in-data-table-in-r
http://stackoverflow.com/questions/15913417/why-does-data-table-update-namesdt-by-reference-even-if-i-assign-to-another-v
Btw, the r-help posting guide says (last time I looked) you should only
post to r-help about packages if you have tried the maintainer first but
didn't hear from them; i.e., r-help isn't for support about packages.
I don't follow r-help, so please continue to cc me if you reply.
Matthew
On 25/09/13 00:47, Jonathan Dushoff wrote:
I got bitten badly when a variable I created for the purpose of
recording an old set of names changed when I didn't think I was going
near it.
I'm not sure if this is a desired behaviour, or documented, or warned
about. I read the data.table intro and the FAQ, and also ?setnames.
Ben Bolker created a minimal reproducible example:
library(data.table)
DT = data.table(x=rep(c("a","b","c"),each=3), y=c(1,3,6), v=1:9)
names(DT)
## [1] "x" "y" "v"
oldnames <- names(DT)
print(oldnames)
## [1] "x" "y" "v"
setnames(DT, LETTERS[1:3])
print(oldnames)
## [1] "A" "B" "C"
______________________________________________
R-help@r-project.org mailing list
https://stat.ethz.ch/mailman/listinfo/r-help
PLEASE do read the posting guide http://www.R-project.org/posting-guide.html
and provide commented, minimal, self-contained, reproducible code.
