On 29/12/2023 9:13 a.m., Mateo Obregón 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?
I don't know if this is a change, but when `eval()` is passed an
expression vector, it evaluates the elements in order and returns the
value of the last one. This is only partially documented:
"Value: The result of evaluating the object: for an expression vector
this is the result of evaluating the last element."
That text has been unchanged in the help page for 13 years.
Duncan Murdoch
______________________________________________
R-devel@r-project.org mailing list
https://stat.ethz.ch/mailman/listinfo/r-devel
