R help - Feb 2022 - [External] Convert a character string to variable names

> 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"

Awesome, thank you so much!

Sincerely,
Erin

Erin Hodgess, PhD
mailto: erinm.hodgess at gmail.com


On Mon, Feb 7, 2022 at 4:05 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$cyl"
>
>
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I assume that the mtcars components were used only as an example, as you
could convert them to a matrix via as.matrix(). Unfortunately, it was a bad
choice: as.name("x$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"
>
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