[R] how to rename variables by lopping off first 3 characters

[Avi Gross]

As R packages are frowned on by some, may I suggest 
a rather trivial base R solution like:

names(mydf) <- sub("^i[.][.]", "", names(mydf))

To be clear, the request is not about general R variable but about 
the names of columns in a data.frame or tibble so all you need to
do in your simple scenario is make some regular expression that
matches only you specified string of "i.." at the beginning of each
word and then use sub() to replace it with nothing. Give it an argument
that contains the current names in your data.frame and save the selectively
shortened results as the new names.

And, yes, dplyr keeps evolving ever more general ways to do
things and those are fine too.

Of course not all changes of this kind can be made by finding a regular
expression.


-----Original Message-----
From: Stefan Schreiber <sschreib using ualberta.ca>
To: Christopher W Ryan <cryan using binghamton.edu>
Cc: R-help <R-help using r-project.org>
Sent: Mon, Mar 14, 2022 1:07 pm
Subject: Re: [R] how to rename variables by lopping off first 3 characters

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 using 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]]
>
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