Bert Gunter
2022-Feb-07 23:21 UTC
[R] [External] Convert a character string to variable names
I assume that the mtcars components were used only as an example, as you
could convert them to a matrix via as.matrix(). Unfortunately, it was a bad
choice: as.name("x$something") is not the name of 'something'
in the data
frame (or list) x. Moreover, as.name("x") does not point to an object
x --
as Rich indicated, it has to be evaluated to do so.> x<- 1:10
> z <- as.name("x")
> z
x> length(z)
[1] 1> eval(z)
[1] 1 2 3 4 5 6 7 8 9 10
But more to the point, I think you are attempting to drive from Brooklyn to
New York City by way of Los Angeles. If I understand correctly, I think all
you need is ?get:
> x <- runif(5)
> y <- 1:5
> z <- 21:25
> nm <- c('x', 'y','z')
> sapply(nm, get)
x y z
[1,] 0.99602479 1 21
[2,] 0.97458756 2 22
[3,] 0.09496625 3 23
[4,] 0.91444550 4 24
[5,] 0.68331484 5 25
Cheers,
Bert Gunter
"The trouble with having an open mind is that people keep coming along and
sticking things into it."
-- Opus (aka Berkeley Breathed in his "Bloom County" comic strip )
On Mon, Feb 7, 2022 at 3:06 PM Richard M. Heiberger <rmh at temple.edu>
wrote:
> > x <- c("mtcars$disp", "mtcars$hp",
"mtcars$cyl")
> > x
> [1] "mtcars$disp" "mtcars$hp" "mtcars$cyl"
> > eval(parse(text=x))
> [1] 6 6 4 6 8 6 8 4 4 6 6 8 8 8 8 8 8 4 4 4 4 8 8 8 8 4 4 4 8 6 8 4
> > for (i in x) print(eval(parse(text=i)))
> [1] 160.0 160.0 108.0 258.0 360.0 225.0 360.0 146.7 140.8 167.6 167.6
> 275.8 275.8 275.8 472.0 460.0 440.0 78.7 75.7 71.1 120.1 318.0
> [23] 304.0 350.0 400.0 79.0 120.3 95.1 351.0 145.0 301.0 121.0
> [1] 110 110 93 110 175 105 245 62 95 123 123 180 180 180 205 215 230
> 66 52 65 97 150 150 245 175 66 91 113 264 175 335 109
> [1] 6 6 4 6 8 6 8 4 4 6 6 8 8 8 8 8 8 4 4 4 4 8 8 8 8 4 4 4 8 6 8 4
>
>
> > On Feb 07, 2022, at 17:55, Erin Hodgess <erinm.hodgess at
gmail.com> wrote:
> >
> >> .x
> >
> > [1] "mtcars$disp" "mtcars$hp"
"mtcars$cyl"
>
> ______________________________________________
> R-help at r-project.org mailing list -- To UNSUBSCRIBE and more, see
> 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.
>
[[alternative HTML version deleted]]
Rui Barradas
2022-Feb-07 23:36 UTC
[R] [External] Convert a character string to variable names
Hello, But that doesn't work in the OP's case: sapply(.x, get) #Error in FUN(X[[i]], ...) : object 'mtcars$disp' not found Like you say, as.name(x$something) is not the name of an object. Hope this helps, Rui Barradas ?s 23:21 de 07/02/2022, Bert Gunter escreveu:> I assume that the mtcars components were used only as an example, as you > could convert them to a matrix via as.matrix(). Unfortunately, it was a bad > choice: as.name("x$something") is not the name of 'something' in the data > frame (or list) x. Moreover, as.name("x") does not point to an object x -- > as Rich indicated, it has to be evaluated to do so. >> x<- 1:10 >> z <- as.name("x") >> z > x >> length(z) > [1] 1 >> eval(z) > [1] 1 2 3 4 5 6 7 8 9 10 > > But more to the point, I think you are attempting to drive from Brooklyn to > New York City by way of Los Angeles. If I understand correctly, I think all > you need is ?get: > >> x <- runif(5) >> y <- 1:5 >> z <- 21:25 >> nm <- c('x', 'y','z') >> sapply(nm, get) > x y z > [1,] 0.99602479 1 21 > [2,] 0.97458756 2 22 > [3,] 0.09496625 3 23 > [4,] 0.91444550 4 24 > [5,] 0.68331484 5 25 > > Cheers, > Bert Gunter > > "The trouble with having an open mind is that people keep coming along and > sticking things into it." > -- Opus (aka Berkeley Breathed in his "Bloom County" comic strip ) > > > On Mon, Feb 7, 2022 at 3:06 PM Richard M. Heiberger <rmh at temple.edu> wrote: > >>> x <- c("mtcars$disp", "mtcars$hp", "mtcars$cyl") >>> x >> [1] "mtcars$disp" "mtcars$hp" "mtcars$cyl" >>> eval(parse(text=x)) >> [1] 6 6 4 6 8 6 8 4 4 6 6 8 8 8 8 8 8 4 4 4 4 8 8 8 8 4 4 4 8 6 8 4 >>> for (i in x) print(eval(parse(text=i))) >> [1] 160.0 160.0 108.0 258.0 360.0 225.0 360.0 146.7 140.8 167.6 167.6 >> 275.8 275.8 275.8 472.0 460.0 440.0 78.7 75.7 71.1 120.1 318.0 >> [23] 304.0 350.0 400.0 79.0 120.3 95.1 351.0 145.0 301.0 121.0 >> [1] 110 110 93 110 175 105 245 62 95 123 123 180 180 180 205 215 230 >> 66 52 65 97 150 150 245 175 66 91 113 264 175 335 109 >> [1] 6 6 4 6 8 6 8 4 4 6 6 8 8 8 8 8 8 4 4 4 4 8 8 8 8 4 4 4 8 6 8 4 >> >> >>> On Feb 07, 2022, at 17:55, Erin Hodgess <erinm.hodgess at gmail.com> wrote: >>> >>>> .x >>> >>> [1] "mtcars$disp" "mtcars$hp" "mtcars$cyl" >> >> ______________________________________________ >> R-help at r-project.org mailing list -- To UNSUBSCRIBE and more, see >> 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. >> > > [[alternative HTML version deleted]] > > ______________________________________________ > R-help at r-project.org mailing list -- To UNSUBSCRIBE and more, see > 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.