[R] [External] Convert a character string to variable names

[Bert Gunter]

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 using 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 using gmail.com> wrote:
> >
> >> .x
> >
> > [1] "mtcars$disp" "mtcars$hp"   "mtcars$cyl"
>
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