Message-ID: <971536df0901120815m6ced77b8v14b57a4df04ccfb9@mail.gmail.com>
Date: 2009-01-12T16:15:06Z
From: Gabor Grothendieck
Subject: assign a list using expression?
In-Reply-To: <496B68A6.5070309@uni-hamburg.de>
This still isn't clear. In your post, values is already
a list with the required names and values in it so the
whole exercise is pointless -- you are starting
out with the answer.
Just guessing, but maybe your setup is a set of variables
in your workspace and a vector of their names with the
output being a named list of them:
a <- 1:2; b <- 1:3
nms <- c("a", "b")
sapply(nms, get, simplify = FALSE)
On Mon, Jan 12, 2009 at 10:58 AM, Skotara <nils.skotara at uni-hamburg.de> wrote:
> Thank you Patrick and Gabor!
> Sorry, I think I have not explainend it well.
> The purpose is as follows:
> names <- letters[1:3]
> values <- data.frame(a = 1:3, b = 4:6, c = 7:9)
> With more complicated objects similar to 'names' and 'values' I wrote the
> following line to assign the elements of the list:
> mycommand <- parse(text = paste(names, " = values[\"", names, "\"]",
> sep="") )
> However,
> list(eval(mycommand))
> does not do what I want.
> whereas
> list(a = values["a"], b = values["b"], c = values["c"])
> does.
>
> I can not tell why...
> I try to understand, what expression and eval do. I know that many times
> there are other ways to achieve the same goal.
> So here, too. But I think there should be a reason why it does not work that
> way.
>
> Best regards!
> Nils
>