[R] Why R >= 4.1 warns about installing Rtools on Windows?

[Samuel Granjeaud]

Hi,

Martin M. helped me focussing the context of my question.  The main 
result of my trials (various R4.x installations) after his mail is that 
the warning is issued when using *devtools* to install a package *from 
github*. When installing a package with install.packages(), no warning.

The warning looks like:

devtools::install_github("i-cyto/cytoBatchNorm")
WARNING: Rtools is required to build R packages, but no version of 
Rtools compatible with R 4.2.1 was found. (Only the following 
incompatible version(s) of Rtools were found: 4.0)
Please download and install Rtools 4.2 from 
https://cran.r-project.org/bin/windows/Rtools/ or 
https://www.r-project.org/nosvn/winutf8/ucrt3/.
Downloading GitHub repo i-cyto/cytoBatchNorm using HEAD
...

I don't think there is a need of Rtools. Let me know if you think there 
is a need of Rtools being installed prior to installing a pure R 
package. From your answers, I may contact the maintainer of devtools.

Thanks for reading.

Bonne journée,
Samuel