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

[Mateo Obregón]

Thanks Gabor, I like your solution that splits the args into separate columns, 
in turn making the sprintf() call more interpretable .

Cheers.

Mateo.
--  
Mateo Obregón
On Friday, 29 December 2023 18:45:06 GMT Gabor Grothendieck 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
> > 
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