[R] order and rm()

Peter Wolf pwolf at wiwi.uni-bielefeld.de
Tue Nov 19 09:08:08 CET 2002

Jess Balint wrote:

>Hello all. I have two small questions in one post, for the sake of
>1. I have some objects that I want to delete. I have the line:
>rm (c (channelheader, paste ("channel", 1:3, sep="")))
>I have tried a few variations, including list=, but cannot figure it
out. In
>SAS, I can use a ':' as a wildcard. Is there any equivalent in R?
>2. Is there any possible was to order data by the second to last

1. # to remove all objects whose names starts by "xyz" followed by a
digit use:
> remove(list=ls(pattern="^xyz[0-9]"))

See: ->  help(ls) -> use of argument "pattern" -> regular expressions
Take care: wild characters / regular expressions are dangerous in
removal processes

2. # to sort a vector of strings by the last and the last but one
> a<-c("asdf","wdftwsertwret","wer","XYCVV")
> a[order((substring(a,nchar(a)-1)))]
> [1] "XYCVV"         "asdf"          "wer"           "wdftwsertwret"

Peter Wolf

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