I think (!!!) I have managed to install R studio. I downloaded the "deb" file and then executed
sudo apt install ./rstudio-1.4.1717-amd64.deb
I then found "Rstudio" in Applications -> Programming in my Mate desktop. When I clicked on "Rstudio" I got the message
R doc dir (/usr/local/lib64/R/doc) not found.
And indeed it is not there.
I should add that /usr/local/lib64/R is a symbolic link to /usr/lib/R.
The latter is where R seems to get installed on my system; the former seems to be where Rstudio wants it to be installed. Initially when I tried to start Rstudio after installing it, I got the complaint that it couldn't find R, so I created the symbolic link.
Anyway, there seems not to be a "docs" directory in my installation of R, and Rstudio demands that there be one. What can I do?