R help - Mar 2022 - how to rename variables by lopping off first 3 characters

I have data coming to me from another source, in which some of the variable
names begin with "i.."

As in "i..actual_meaningful_var_name"

I would like to remove the first three characters from any variable name if
they are "i.."

I'm using R on Win 10 and dplyr, so ideally I'm looking for a dplyr
solution. Apparently I'm just not understanding how the various select,
contains, rename_at, rename_with, and so-on dplyr expressions work. I've
tried various arrangements of them, usually resulting in

Error: `contains()` must be used within a *selecting* function.
i See <https://tidyselect.r-lib.org/reference/faq-selection-context.html>

A simple select(contains(foo)) I can do fine, to select a subset of
variables. It's combining it with renaming that I am struggling with.

Grateful for any advice.

Thanks.

--Chris Ryan

	[[alternative HTML version deleted]]

This should work (couldn't check - not at my computer right now):

my_df %<% rename_at(vars(starts_with("i..")), funs(str_replace(.,
"i..",
"")))

There are also a lot of tutorials on the internet. Google something like
"rename_at str_replace"

HTH,
Stefan

On Mon, Mar 14, 2022, 10:27 Christopher W Ryan via R-help, <
r-help at r-project.org> wrote:
> I have data coming to me from another source, in which some of the variable
> names begin with "i.."
>
> As in "i..actual_meaningful_var_name"
>
> I would like to remove the first three characters from any variable name if
> they are "i.."
>
> I'm using R on Win 10 and dplyr, so ideally I'm looking for a dplyr
> solution. Apparently I'm just not understanding how the various select,
> contains, rename_at, rename_with, and so-on dplyr expressions work.
I've
> tried various arrangements of them, usually resulting in
>
> Error: `contains()` must be used within a *selecting* function.
> i See
<https://tidyselect.r-lib.org/reference/faq-selection-context.html>
>
> A simple select(contains(foo)) I can do fine, to select a subset of
> variables. It's combining it with renaming that I am struggling with.
>
> Grateful for any advice.
>
> Thanks.
>
> --Chris Ryan
>
>         [[alternative HTML version deleted]]
>
> ______________________________________________
> R-help at r-project.org mailing list -- To UNSUBSCRIBE and more, see
> https://stat.ethz.ch/mailman/listinfo/r-help
> PLEASE do read the posting guide
> http://www.R-project.org/posting-guide.html
> and provide commented, minimal, self-contained, reproducible code.
>
	[[alternative HTML version deleted]]

If you care to entertain this, one of many simple base R ways to do this is:

dat <- data.frame(
+    i..One = 1:3,
+    i..Two = letters[1:3],
+    ixx = 5:7)
> dat
  i..One i..Two ixx
1      1      a   5
2      2      b   6
3      3      c   7
> nm <- names(dat)
> nm <- ifelse(substring(nm, 1,3) == "i..",
+              substring(nm,4),
+              nm)
> names(dat) <- nm
> dat
  One Two ixx
1   1   a   5
2   2   b   6
3   3   c   7

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, Mar 14, 2022 at 9:27 AM Christopher W Ryan via R-help
<r-help at r-project.org> wrote:
>
> I have data coming to me from another source, in which some of the variable
> names begin with "i.."
>
> As in "i..actual_meaningful_var_name"
>
> I would like to remove the first three characters from any variable name if
> they are "i.."
>
> I'm using R on Win 10 and dplyr, so ideally I'm looking for a dplyr
> solution. Apparently I'm just not understanding how the various select,
> contains, rename_at, rename_with, and so-on dplyr expressions work.
I've
> tried various arrangements of them, usually resulting in
>
> Error: `contains()` must be used within a *selecting* function.
> i See
<https://tidyselect.r-lib.org/reference/faq-selection-context.html>
>
> A simple select(contains(foo)) I can do fine, to select a subset of
> variables. It's combining it with renaming that I am struggling with.
>
> Grateful for any advice.
>
> Thanks.
>
> --Chris Ryan
>
>         [[alternative HTML version deleted]]
>
> ______________________________________________
> R-help at r-project.org mailing list -- To UNSUBSCRIBE and more, see
> https://stat.ethz.ch/mailman/listinfo/r-help
> PLEASE do read the posting guide
http://www.R-project.org/posting-guide.html
> and provide commented, minimal, self-contained, reproducible code.

Hello,

I have already seen those names starting with 'i..' several times but I 
don't remember where nor why.
I think it has to do with encoding. Or maybe special characters. I have 
the impression that the best solution was to read the data in a way as 
to avoid the problem.

Using Bert's example data set, here are base R and tidyverse solutions.


dat <- data.frame(
   i..One = 1:3,
   i..Two = letters[1:3],
   ixx = 5:7)

# base R
names(dat) <- sub("^i\\.\\.", "", names(dat))
names(dat)

# tidyverse
dplyr::rename_with(dat, .fn = \(x) sub("^i\\.\\.", "", x), 
starts_with("i.."))


Hope this helps,

Rui Barradas

?s 16:26 de 14/03/2022, Christopher W Ryan via R-help
escreveu:
> I have data coming to me from another source, in which some of the variable
> names begin with "i.."
> 
> As in "i..actual_meaningful_var_name"
> 
> I would like to remove the first three characters from any variable name if
> they are "i.."
> 
> I'm using R on Win 10 and dplyr, so ideally I'm looking for a dplyr
> solution. Apparently I'm just not understanding how the various select,
> contains, rename_at, rename_with, and so-on dplyr expressions work.
I've
> tried various arrangements of them, usually resulting in
> 
> Error: `contains()` must be used within a *selecting* function.
> i See
<https://tidyselect.r-lib.org/reference/faq-selection-context.html>
> 
> A simple select(contains(foo)) I can do fine, to select a subset of
> variables. It's combining it with renaming that I am struggling with.
> 
> Grateful for any advice.
> 
> Thanks.
> 
> --Chris Ryan
> 
> 	[[alternative HTML version deleted]]
> 
> ______________________________________________
> R-help at r-project.org mailing list -- To UNSUBSCRIBE and more, see
> https://stat.ethz.ch/mailman/listinfo/r-help
> PLEASE do read the posting guide
http://www.R-project.org/posting-guide.html
> and provide commented, minimal, self-contained, reproducible code.