[Rd] eval(parse()) within mutate() returning same value for all rows

[Gabor Grothendieck]

Here is a solution that does not hard code 3:

  library(dplyr)
  library(purrr)
  library(tidyr)

  df %>%
     separate_wider_delim(args, ",", names_sep = "") %>%
     mutate(combined = exec(sprintf, .[[1]], !!!.[-1]))
  ## # A tibble: 3 × 5
  ## words                args1 args2 args3 combined
  ## <chr>                <chr> <chr> <chr> <chr>
  ## 1 %s plus %s equals %s 1     1     2     1 plus 1 equals 2
  ## 2 %s plus %s equals %s 2     2     4     2 plus 2 equals 4
  ## 3 %s plus %s equals %s 3     3     6     3 plus 3 equals 6

On Fri, Dec 29, 2023 at 1:45 PM Gabor Grothendieck
<ggrothendieck using gmail.com> wrote:
>
> If the question is how to accomplish this as opposed to how to use eval
> then we can do it without eval like this provided we can assume that words
> contains three %s .
>
>   library(dplyr)
>   library(tidyr)
>   df <- tibble(words=c("%s plus %s equals %s"),args=c("1,1,2","2,2,4","3,3,6"))
>
>   df |>
>     separate_wider_delim(args, ",", names = c("a", "b", "c")) |>
>     mutate(combined = sprintf(words, a, b, c))
>   ## # A tibble: 3 × 5
>   ## words                a     b     c     combined
>   ## <chr>                <chr> <chr> <chr> <chr>
>   ## 1 %s plus %s equals %s 1     1     2     1 plus 1 equals 2
>   ## 2 %s plus %s equals %s 2     2     4     2 plus 2 equals 4
>   ## 3 %s plus %s equals %s 3     3     6     3 plus 3 equals 6
>
> On Fri, Dec 29, 2023 at 9:14 AM Mateo Obregón <obregonmateo using gmail.com> wrote:
> >
> > Hi all-
> >
> > Looking through stackoverflow for R string combining examples, I found the
> > following from 3 years ago:
> >
> > <https://stackoverflow.com/questions/63881854/how-to-format-strings-using-values-from-other-column-in-r>
> >
> > The top answer suggests to use eval(parse(sprintf())). I tried the suggestion
> > and it did not return the expected combines strings. I thought that this might
> > be an issue with some leftover values being reused, so I explicitly eval()
> > with a new.env():
> >
> > > library(dplyr)
> > > df <- tibble(words=c("%s plus %s equals %s"),
> > args=c("1,1,2","2,2,4","3,3,6"))
> > > df |> mutate(combined = eval(parse(text=sprintf("sprintf('%s', %s)", words,
> > args)), envir=new.env()))
> >
> > # A tibble: 3 × 3
> >   words                args  combined
> >   <chr>                <chr> <chr>
> > 1 %s plus %s equals %s 1,1,2 3 plus 3 equals 6
> > 2 %s plus %s equals %s 2,2,4 3 plus 3 equals 6
> > 3 %s plus %s equals %s 3,3,6 3 plus 3 equals 6
> >
> > The `combined`  is not what I was expecting, as the same last eval() is
> > returned for all three rows.
> >
> > Am I missing something? What has changed in the past three years?
> >
> > Mateo.
> > --
> > Mateo Obregón
> >
> > ______________________________________________
> > R-devel using r-project.org mailing list
> > https://stat.ethz.ch/mailman/listinfo/r-devel
>
>
>
> --
> Statistics & Software Consulting
> GKX Group, GKX Associates Inc.
> tel: 1-877-GKX-GROUP
> email: ggrothendieck at gmail.com



-- 
Statistics & Software Consulting
GKX Group, GKX Associates Inc.
tel: 1-877-GKX-GROUP
email: ggrothendieck at gmail.com